U.S. patent application number 13/379114 was filed with the patent office on 2012-05-17 for photoelectric element.
Invention is credited to Sakoto Kambe, Shingo Kambe, Fumiaki Kato, Hiroyuki Nishide, Kenichi Oyaizu, Takashi Sekiguchi, Michio Suzuka, Mitsuo Yaguchi, Takeyuki Yamaki.
Application Number | 20120119193 13/379114 |
Document ID | / |
Family ID | 43356478 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120119193 |
Kind Code |
A1 |
Sekiguchi; Takashi ; et
al. |
May 17, 2012 |
PHOTOELECTRIC ELEMENT
Abstract
A photoelectric element provided with an electron transport
layer having excellent electron transport property and sufficiently
wide reaction interface, and that has excellent conversion
efficiency. The photoelectric element has an electron transport
layer 3 and a hole transport layer 4 sandwiched between a pair of
electrodes 2 and 5. The electron transport layer 3 is formed of an
organic compound having a redox moiety capable of being oxidized
and reduced repeatedly. The organic compound contains an
electrolyte solution which stabilizes the reduced state of the
redox moiety, and forms a gel layer 6 containing a sensitizing dye.
Thus, the organic compound and the electrolyte solution in the
electron transport layer 3 constitute the gel layer 6, while at the
same time, the sensitizing dye is present within the gel layer 6,
whereby the reaction interface of the organic compound is enlarged,
improving the conversion efficiency and the electron hand-over
efficiency from the sensitizing dye to the organic compound in the
electron transport layer 3, as a result of which the electron
transport efficiency is improved.
Inventors: |
Sekiguchi; Takashi;
(Suita-shi, JP) ; Yaguchi; Mitsuo; (Osaka, JP)
; Yamaki; Takeyuki; (Nara, JP) ; Nishide;
Hiroyuki; (Tokyo, JP) ; Oyaizu; Kenichi;
(Tokyo, JP) ; Kato; Fumiaki; (Tokyo, JP) ;
Suzuka; Michio; (Shijonawate-shi, JP) ; Kambe;
Shingo; (Hirakata-shi, JP) ; Kambe; Sakoto;
(Hirakata-shi, JP) |
Family ID: |
43356478 |
Appl. No.: |
13/379114 |
Filed: |
June 16, 2010 |
PCT Filed: |
June 16, 2010 |
PCT NO: |
PCT/JP2010/060245 |
371 Date: |
December 19, 2011 |
Current U.S.
Class: |
257/40 ;
257/E51.026 |
Current CPC
Class: |
H01L 51/004 20130101;
H01G 9/2027 20130101; H01M 14/005 20130101; H01L 51/005 20130101;
Y02E 10/542 20130101; H01G 9/2004 20130101; H01L 51/0035 20130101;
H01G 9/2059 20130101 |
Class at
Publication: |
257/40 ;
257/E51.026 |
International
Class: |
H01L 51/54 20060101
H01L051/54 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2009 |
JP |
2009-147070 |
Jul 31, 2009 |
JP |
2009-180174 |
Oct 27, 2009 |
JP |
2009-246797 |
Feb 5, 2010 |
JP |
2010-024413 |
Claims
1. A photoelectric element comprising: a pair of electrodes; and an
electron transport layer and a hole transport layer that are
sandwiched between these electrodes, said electron transport layer
comprising an organic compound having a redox moiety capable of
being oxidized and reduced repeatedly, said organic compound being
combined with an electrolyte solution that stabilizes the reduced
state of said redox moiety to form a gel layer, and said gel layer
containing a sensitizing dye.
2. The photoelectric element according to claim 1, wherein the
sensitizing dye is immobilized within the gel layer by a physical
or a chemical action with the organic compound contained within
said gel layer.
3. The photoelectric element according to claim 1, wherein the
open-circuit voltage A (V) at the time point when light at 200 lux
is radiated for 5 minutes and the open-circuit voltage B (V) at the
time point when 5 minutes have elapsed from when the light is
shielded at the above time point, satisfy the following relational
expression: (B/A).times.100.gtoreq.10.
4. The photoelectric element according to claim 1, wherein a redox
potential of the electron transport layer slopes from noble to base
in the direction toward the electrode in contact with this electron
transport.
5. The photoelectric element according to claim 4, wherein the
electron transport layer contains two or more species of said
organic compounds selected from the group consisting of imide
derivatives, quinone derivatives, viologen derivatives and phenoxyl
derivatives.
6. The photoelectric element according to claim 1, wherein the hole
transport layer contains an azaadamantane-N-oxyl derivative
indicated in [Chem. 1] below: ##STR00024## (R.sub.1 and R.sub.2
each independently represents a hydrogen, a fluorine, an alkyl
group or a substituted alkyl group, and X.sub.1 represents a
methylene group or an N-oxyl group indicated in [Chem. 2])
##STR00025##
7. The photoelectric element according to claim 6, wherein the
azaadamantane-N-oxyl derivative contains at least one species
selected from the group consisting of azaadamantane-N-oxyl and
1-methyl-2-azaadamantane-N-oxyl.
8. The photoelectric element according to claim 1, wherein said gel
layer contains an electro-conductive additive at least a portion of
which is in contact with the electrode.
9. The photoelectric element according to claim 8, wherein a
roughness factor of the electro-conductive additive is 5 or greater
but 2,000 or less.
10. The photoelectric element according to claim 8, wherein the
electro-conductive additive is formed of an aggregation of
particles of electro-conductive materials.
11. The photoelectric element according to claim 8, wherein the
electro-conductive additive is formed of a fibrous
electro-conductive material.
12. The photoelectric element according to claim 11, wherein an
average external diameter of the fibrous electro-conductive
material is 50 nm or greater but 1,000 nm or less.
13. The photoelectric element according to claim 11, wherein a
porosity of the electro-conductive additive formed of the fibrous
electro-conductive material is 50% or greater but 95% or less.
14. The photoelectric element according to claim 11, wherein an
average fiber length/average fiber diameter ratio of the fibrous
electro-conductive material is 1,000 or greater.
15. The photoelectric element according to claim 2, wherein the
open-circuit voltage A (V) at the time point when light at 200 lux
is radiated for 5 minutes and the open-circuit voltage B (V) at the
time point when 5 minutes have elapsed from when the light is
shielded at the above time point, satisfy the following relational
expression: (B/A).times.100.gtoreq.10.
Description
TECHNICAL FIELD
[0001] The present invention relates to a photoelectric element for
converting light into electricity.
BACKGROUND ART
[0002] In recent years, a variety of photoelectric elements are
being used, including photoelectrochemical elements such as
photoelectric conversion-based electricity-generating elements
including photovoltaic batteries and solar batteries,
light-emitting elements, electrochromic display elements, optical
display elements such as electron papers, electrochemical elements
such as batteries and electrostatic capacitors, non-volatile
memories and arithmetic elements, electric elements such as
transistors, sensor elements for detecting the
temperature/humidity/amount of light/amount of
heat/pressure/magnetic force or the like.
[0003] Required of an electron transport layer provided in these
photoelectric elements is the property of high electron transport;
in addition, the size of the surface area of the reaction interface
is important, which is where electrons are generated by energies
from outside and where electrons injected from outside act as well.
In prior art, such electron transport layer is formed from metal,
organic semiconductor, inorganic semiconductor, electro-conductive
polymer, electro-conductive carbon or the like.
[0004] For instance, in a photoelectric conversion element, a
electron transport layer for transporting electrons is made from an
organic compound having electron as carriers, such as, fullerene,
peryrene derivatives, polyphenylenevinylene derivatives and
pentacene, the electron transport capabilities of these substances
are improving the conversion efficiency (refer to Non-Patent
Reference 1 regarding fullerene, refer to Non-Patent Reference 2
regarding peryrene derivatives, and refer to Non-Patent Reference 3
regarding polyphenylenevinylene derivatives).
[0005] In addition, in regard to molecular element-type solar
batteries, forming a structure comprising chemically bonded
electron-donating molecule (donor) and electron-accepting molecule
(acceptor) into a thin film over a substrate has also been reported
(refer to Non-Patent Reference 4). [0006] Non-Patent Reference 1:
P. Peumans, Appl. Phys. Lett., No. 79, 2001, p. 126 [0007]
Non-Patent Reference 2: C. W. Tang, Appl. Phys. Lett., No. 48,
1986, p. 183 [0008] Non-Patent Reference 3: S. E. Shaheen, Appl.
Phys. Lett., No. 78, 2001, p. 841 [0009] Non-Patent Reference 4:
"Bunshi Taiyo Denchi no Tenbo (Development of molecular-based solar
cells)" by Hiroshi Imahori, Shunichi Fukuzumi, July 2001 p. 41
(Japan Chemical Industry Association)
DISCLOSURE OF THE INVENTION
[0010] However, the electron transport layers reported in the above
non-patent references do not have simultaneously a sufficient
electron transport property and a sufficiently wide reaction
interface to act as an electron transport layer. Therefore, the
current situation is that an electron transport layer for electron
transport having more excellent electron transport property and
sufficiently wide reaction interface is desired.
[0011] For instance, in the case of an organic electron transport
layer comprising a fullerene or the like, a charge recombination of
the electron being likely to occur, the effective diffusion
distance is not sufficient, such that further improvement of
conversion efficiency is difficult. This effective diffusion
distance refers to the distance until an electrode is reached after
electric charge separation has occurred, and the larger the
effective diffusion distance, the greater the conversion efficiency
of the element. In addition, in the case of an inorganic electron
transport layer such as of titanium oxide, the conversion
efficiency is not sufficient, from such reasons as, the interface
surface area of electric charge separation is not sufficient and
the constituent elements determine unequivocally the electron
conduction potential, which influences the open-circuit
voltage.
[0012] Devised in view of the above problems, it is an object of
the present invention to provide a photoelectric element having
excellent conversion efficiency, provided with an electron
transport layer having excellent electron transport property and
sufficiently wide reaction interface.
[0013] The photoelectric element according to the present invention
comprises a pair of electrodes, and an electron transport layer and
a hole transport layer that are sandwiched between these
electrodes, the electron transport layer comprising an organic
compound having a redox moiety capable of being oxidized and
reduced repeatedly and a gel layer containing the organic compound
and an electrolyte solution that stabilizes the reduced state of
the organic compound and the redox moiety, and a sensitizing dye
being present within the gel layer.
[0014] In the present invention, the organic compound and the
electrolyte solution in the electron transport layer constitute the
gel layer, while at the same time, the sensitizing dye is present
within the gel layer, whereby the reaction interface of the organic
compound is enlarged, improving the conversion efficiency and the
electron hand-over efficiency from the sensitizing dye to the
organic compound in the electron transport layer, as a result of
which the electron transport efficiency is improved.
[0015] The sensitizing dye is preferably immobilized within the gel
layer by a physical or a chemical action with the organic compound
constituting the gel layer.
[0016] In this case, the reaction interface of the electron
transport layer becomes larger, further improving the efficiency of
photoelectric conversion.
[0017] In the photoelectric element according to the present
invention, it is desirable that the open-circuit voltage A (V) at
the time point when light at 200 lux is radiated for 5 minutes and
the open-circuit voltage B (V) at the time point when 5 minutes
have elapsed from when the light is shielded at the above time
point, satisfy the following relational expression:
(B/A).times.100.gtoreq.10.
[0018] In the present invention, a redox potential of the electron
transport layer may slope from noble to base in the direction
toward the electrode in contact with this electron transport.
[0019] In the present invention, the electron transport layer may
contain two or more species of organic compounds selected from
imide derivatives, quinone derivatives, viologen derivatives and
phenoxyl derivatives.
[0020] In the present invention, the hole transport layer 4 may
contain an azaadamantane-N-oxyl derivative indicated in [Chem. 1]
below:
##STR00001##
(R.sub.1 and R.sub.2 each independently represents a hydrogen, a
fluorine, an alkyl group or a substituted alkyl group, and X.sub.1
represents a methylene group or an N-oxyl group indicated in [Chem.
2])
##STR00002##
[0021] In the present invention, the azaadamantane-N-oxyl
derivative may contain at least one species among
azaadamantane-N-oxyl and 1-methyl-2-azaadamantane-N-oxyl.
[0022] In the present invention, an electro-conductive additive is
present within the gel layer, while at least a portion of the
electro-conductive additive may be in contact with the
electrode.
[0023] In the present invention, a roughness factor of the
electro-conductive additive may be 5 or greater but 2,000 or
less.
[0024] In the present invention, the electro-conductive additive
may be formed of an aggregation of particles of electro-conductive
materials.
[0025] In the present invention, the electro-conductive additive
may be formed of a fibrous electro-conductive material.
[0026] In the present invention, an average external diameter of
the fibrous electro-conductive material may be 50 nm or greater but
1,000 nm or less.
[0027] In the present invention, a porosity of the electro
conductive additive formed of the fibrous electro-conductive
material may be 50% or greater but 95% or less.
[0028] In the present invention, an average fiber length/average
fiber diameter ratio of the fibrous electro-conductive material may
be 1,000 or greater.
[0029] According to the present invention, the electron transport
property of the electron transport layer improves while the
reaction interface becomes wide, improving the conversion
efficiency of the photoelectric element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a cross-sectional overview showing an embodiment
of the present invention;
[0031] FIG. 2 is a cross-sectional overview showing a variation
example of the embodiment;
[0032] FIG. 3 is a cross-sectional overview showing a variation
example of the embodiment;
[0033] FIG. 4 is a cross-sectional overviews showing a variation
example the embodiment with (a), (b) and (c) being partial
enlargements;
[0034] FIG. 5 is an electron micrograph of the porous
electro-conductive film in Example 13;
[0035] FIG. 6 is a graph showing the change over time of the
open-circuit voltage for a photoelectric element when light is
radiated onto a photoelectric element obtained in Example 1, and
then shielded; and
[0036] FIG. 7 is a graph showing the change over time of
open-circuit voltage for a photoelectric element when light is
radiated onto a photoelectric element obtained in Comparative
Example 1, and then shielded.
BEST MODE FOR CARRYING OUT THE INVENTION
[0037] Embodiments of the present invention will be described
below.
[0038] As shown in FIG. 1, in the photoelectric element of the
present embodiment, an electron transport layer 3 and a hole
transport layer 4 are sandwiched between a pair of electrodes 2 and
5 (a first electrode 2 and a second electrode 5). The electron
transport layer 3 includes an organic compound having a redox
moiety. This organic-compound is swollen by containing an
electrolyte solution, thereby forming a gel layer 6. That is to
say, the electron transport layer 3 is formed of the organic
compound that has the redox moiety and forms with the electrolyte
solution the gel layer 6 within which the sensitizing dye is
present.
[0039] The first electrode 2 is electrically connected to the
electron transport layer 3 and extracts electrons from the electron
transport layer 3 to the exterior or exerts the function of
injecting electrons into the transport layer 3. In addition, it
also has the function of physically retaining the electron
transport layer 3. The exterior refers to a power circuit, a
secondary battery, a capacitor and the like, which are electrically
connected to the photoelectric element.
[0040] The first electrode 2 may be formed of a single film of
electro-conductive material such as metal; in addition, an
electro-conductive material may be layered over an insulating first
substrate 1 such as glass or a film, whereby the first electrode 2
is formed on the first substrate 1. As preferred examples of
electro-conductive materials, metals such as platinum, gold,
silver, copper, aluminum, rhodium and indium; electro-conductive
metal oxides such as carbon; indium-tin complex oxide, tin oxide
doped with antimony and tin oxide doped with fluorine; complexes of
the above metals or compounds; materials comprising silicon oxide,
tin oxide, titanium oxide, zirconium oxide, aluminum oxide, or the
like, coated over the above metals or compounds, and the like, may
be cited. While the lower the surface resistance of the first
electrode 2, the better, preferably, the surface resistance is
200.OMEGA./.quadrature. or lower, and more preferably
50.OMEGA./.quadrature. or lower. While there is no particular
restriction on the lower limit of this surface resistance, it is in
general 0.1.OMEGA./.quadrature..
[0041] The first electrode 2 may have optical transparency. In this
case, light from the outside may be injected into the photoelectric
element 1 through this first electrode 2. It is desirable that the
first electrode 2 is transparent so as to allow light to be
transmitted. In this case, the first electrode 2 is formed for
instance of a transparent electro-conductive material or the like.
In addition, the first electrode 2 may have an opening, so that the
first electrode 2 allows light to be transmitted via the opening.
As the opening formed in the first electrode 2, for instance,
opening in the form of a slit or in the form of a hole may be
cited. The shape of the opening in the form of a slit may be any
shape such as a straight line, a wave line or a grid.
Electro-conductive particles may be arranged to form the first
electrode 2, while at the same time, openings may be formed between
these electro-conductive particles. When the first electrode 2
having such openings is formed, a transparent electro-conductive
material becomes unnecessary, allowing for a reduction of material
costs.
[0042] When the first electrode 2 is transparent, the higher the
light transmittance of the first electrode 2, the better. The
preferred range of light transmittance for the first electrode 2 is
50% or greater, and more preferably 80% or greater. The thickness
of the first electrode 2 is preferably in the range of 1 to 100 nm.
The reason is that, if the thickness is in this range, an electrode
film having a uniform film-thickness can be formed, and in
addition, sufficient light can be injected into the electron
transport layer 3 without decreasing the optical transparency of
the first electrode 2. When a transparent first electrode 2 is
used, light is preferably injected from this first electrode 2 on
the side where the electron transport layer 3 is deposited.
[0043] In forming the first electrode 2 over the first substrate 1,
when the photoelectric element requires light to pass through the
first substrate 1 similarly to an electricity-generating element, a
light-emitting element, a light sensor, or the like, it is
desirable that the light transmittance of the first substrate 1 is
high. The preferred light transmittance in this case is 50% or
greater at a wavelength of 500 nanometers, and more preferably 80%
or greater. In addition the thickness of the first electrode 2 is
preferably within the range of 0.1 to 10 .mu.m. Within this range,
the first electrode 2 can be formed with a uniform thickness, in
addition a drop in optical transparency of the first electrode 2
can be suppressed, allowing sufficient light to be injected through
the first electrode 2 into the electron transport layer 3.
[0044] When forming the first electrode 2 by providing a layer of
transparent electro-conductive oxide over a first substrate 1, for
instance, a vacuum process such as sputter method or vapor
deposition method may be used over a light-transmitting substrate
comprising glass, resin, or the like, or, a layer of transparent
electro-conductive oxide comprising indium oxide, tin oxide, zinc
oxide, or the like, may be formed into a film by a wet method such
as spincoat method, spray method or screen printing to form the
first electrode 2.
[0045] The organic compound constituting the electron transport
layer 3 has, as an intramolecular portion thereof, a redox moiety
capable of being oxidized and reduced repeatedly, and at the same
time, has as another portion, a domain that swells to become a gel
(gel domain) by including an electrolyte solution. The redox moiety
is chemically bonded to the gel domain. While the positional
relationship within the molecule between the redox moiety and the
gel domain is not limited in particular, for instance, when a
backbone such as the main chain of the molecule is formed with the
gel domain, the redox moiety is bonded to the main chain as a side
chain. In addition, a structure in which a molecular backbone
forming a gel domain and a molecular backbone forming a redox
moiety are alternately bonded is also adequate. When a redox moiety
and a gel domain are present within one identical molecule of
organic compound in this manner, the redox moiety can be retained
in the gel layer 6 forming the electron transport layer 3 so as to
remain at a location where transporting electrons is
straightforward.
[0046] The organic compound having the redox moiety and the gel
domain may be a small molecule or a macromolecule. When it is a
small molecule, an organic compound forming a so-called small
molecule gel through hydrogen bonds, or the like, can be used. In
addition, in the case of a macromolecule, an organic compound
having a number average molecular weight of 1,000 or greater is
desirable, as it can spontaneously exert the function of gelation.
Although the upper limit of the molecular weight of the organic
compound in the case of a macromolecule is not limited in
particular, 1,000,000 or less is desirable. In addition, it is
desirable that the state of the gel in the gel layer 6 is, for
instance, the form of a konjac food or a form similar to an ion
exchange film in external appearance, although there is no
particular limitation.
[0047] In addition, the redox moiety designates a domain that
reversibly becomes an oxidant and a reductant in an oxido-reduction
reaction. In addition, the redox moiety is preferably a substance
constituting an oxido-reduction system in which the oxidant and the
reductant have an identical electric charge.
[0048] Thusly, since the electron transport layer 3 is provided
with an organic compound having a redox moiety capable of being
oxidized and reduced repeatedly and, moreover, the organic compound
contains an electrolyte solution that stabilizes the reduced state
of the redox moiety, the electron transport layer 3, which, formed
as the gel layer 6, allows the structure to be fragmented at the
molecule level, can have the reaction interface enlarged, and can
transport electrons efficiently and at a rapid reaction rate.
[0049] Here, oxido-reduction (oxido-reduction reaction) refers to
an ion, an atom or a compound donating and accepting an electron,
and redox moiety refers to a domain that can stably donate and
accept an electron by oxido-reduction reaction (redox
reaction).
[0050] In addition, gel layer 6 refers to a layer formed by an
organic compound having a redox moiety being swollen with an
electrolyte solution. That is to say, in the gel state, the organic
compound adopts a three-dimensional network structure, and a layer
in a state in which the interior of this network is filled with
liquid is referred to as the gel layer 6.
[0051] Forming the gel layer 6 by swelling the organic compound
having the redox moiety with an electrolyte solution in this way
allows the redox moiety to be retained in the vicinity of the first
electrode 2 and the organic compound to be retained in such a way
that redox moieties that are next to each other are at a distance
that is sufficiently close to exchange an electron among them. In
addition, redox moieties can exist at a high density in the
electron transport layer 3 which can realize an extremely rapid
electron self-exchange reaction rate constant, allowing the
electron transport capability to be raised. Furthermore, forming
the electron transport layer 3 as an organic compound gel layer 6
facilitates giving the electron transport layer 3 adhesiveness or
giving the electron transport layer 3 flexibility or optical
transparency.
[0052] In addition, since the redox moiety is present within the
molecule of organic compound forming the gel layer 6 as described
above, retention of the redox moiety by the gel layer 6 in a state
in which electron transport by the repetition of oxido-reduction
reaction is more effectively carried out is facilitated. That is to
say, since the redox moiety is chemically bonded to the organic
compound forming the gel layer 6, the redox moiety can be retained
with the gel layer 6 so as to remain at a position where
transporting electron is straight forward. The positional
relationship of the redox moiety within the organic compound may
be, for instance, a structure in which the redox moiety is arranged
as a side chain with respect to the backbone of the organic
compound forming the gel layer 6, or the backbone of the organic
compound and the redox moiety may be bonded by being arranged
alternately or partially continuously.
[0053] Then, the redox moiety is one that can transport electrons
by electron exchange reaction between redox moieties, and not by
diffusion. This electron exchange reaction is a reaction in which a
redox moiety in an oxidized state oxidizes a neighboring redox
moiety in a reduced state, exchanging an electron among the redox
moieties, whereby, in appearance, an electron is transported within
the layer of the electron transport layer 3. While the function
resembles that of an ion conductive material in which ions are
transmitted by diffusion, the electron transport mechanism in the
electron transport layer 3 of the present embodiment is different
on the point that the redox moieties transport electrons by
exchange with neighboring redox moieties, not by diffusion. While
the redox moieties need to be near one another also in the electron
transport layer 3 of the present embodiment in order to hand an
electron over to a neighboring redox moiety so as to allow for
electron displacements, since the redox moiety is retained by the
gel layer 6, the distance of displacement is expected to be few
angstroms. In particular, when the redox moiety is present within a
molecule of organic compound forming the gel layer 6 as in the
present embodiment, the reaction of electron exchange with a
neighboring redox moiety is a reaction called electron
self-exchange reaction.
[0054] While a photoelectric conversion element provided with a
solid ion conductor containing an oxido-reduction system in a
macromolecular compound is described in Japanese Patent Application
Laid-open No. H07-288142, this ion conductor is a hole transport
material, not an electron transport material.
[0055] In the electron transport layer 3 of the photoelectric
element of the present embodiment, by retaining the redox moiety in
the gel layer 6 as described above, the field of the reaction for
converting light into electricity or electricity into light, that
is to say, the reaction interface, can be enlarged without
compromising electron transportability, allowing a photoelectric
element having high conversion efficiency to be obtained.
[0056] The reaction interface here refers to the interface between
the electron transport layer 3 and a hole transport material or the
electrolyte solution. For instance, since electric charges
generated by light absorption are separated at the reaction
interface in a photoelectric conversion element, the wider the
reaction interface the higher the conversion efficiency, and in
contrast to prior art where the surface area of the reaction
interface could not be enlarged sufficiently, with the present
embodiment, since the gel layer 6 is formed by including the
electrolyte solution in the organic compound having the redox
moiety as described above, the reaction interface between the redox
moiety and the electrolyte solution that penetrated the electron
transport layer 3 becomes large, allowing the conversion efficiency
to be raised. The following two points are considered as reasons
for the reaction interface to be enlarged. The first is the
consideration that, with an electron transport material comprising
a prior art inorganic semiconductor or the like, even if it is
turned into a microparticle, reaching sub-nanometer scale is
difficult due to the material being inorganic, while, in contrast,
the electron transport layer 3 of the present embodiment allows the
structure to be fragmented at the molecular level if the redox
moiety is in a state that can undergo oxido-reduction and transport
electrons, which allows the surface area of the interface needed
for electric charge separation to be increased. In particular, when
the electron transport layer 3 is formed from a macromolecular
organic compound, angstrom-scale interface formation is possible,
theoretically. As the second reason, the possibility is considered
that, at the interface between the redox moiety of the organic
compound constituting the electron transport layer 3 and the hole
transport layer 4, the electrolyte solution, or the like, a special
interface state is formed, which may promote electric charge
separation.
[0057] In addition, since the electron transport layer 3 is formed
with an organic compound having a redox moiety, design or synthesis
according to electrical properties such as electric potential or
structural properties such as molecule size is facilitated, and
furthermore, the control, or the like, of gelation or solubility is
possible. In addition, since the electron transport layer 3 is
formed with an organic compound, high temperature firing such as
when forming a layer of electron transport material with an
inorganic material such as an inorganic semiconductor is
unnecessary, which is an advantage in the manufacturing process,
and in addition, the electron transport layer 3 can be rendered
flexible. In addition, the facts that, unlike inorganic materials
and noble metal materials, the organic compound has no problem of
resource depletion, has low toxicity, allows heat energy to be
recovered by incineration when being discarded, and the like, can
also be cited as advantages.
[0058] Furthermore, in the present embodiment, the organic compound
forming the electron transport layer 3 contains an electrolyte
solution as described above, thereby allowing the reduced state of
the redox moiety present within the organic compound to be
stabilized, and allowing electrons to be transported more stably.
That is to say, while organic compounds are considered difficult to
use as materials for the electron transport layer 3 since the
reduced state is unstable compared to inorganic compounds such as
metal semiconductors and metal oxide semiconductors which are
generally used as electron transport materials, by giving a
structure that contains an electrolyte solution, the ionic state
formed by the oxido-reduction reaction of the redox moiety is
compensated by counter-ions in the electrolyte solution, that is to
say, for instance, a redox moiety turned into a cationic state is
stabilized by the opposite electric charge from an anion in the
electrolyte solution, furthermore, the reduced state can be
stabilized by the action of the solvent such as solvation or
dipolar moment, which, as a result, can stabilize the redox
moiety.
[0059] Here, a physical index of the gel layer 6 that has an
influence on the size of the reaction interface is the swelling
degree. The swelling degree mentioned here is represented by the
following formula:
Swelling degree (%)=(weight of gel)/(weight of dried
gel).times.100
[0060] A dried gel designates a gel that has been dried. This
drying of gel designates the removal of the solution included in
the gel, and in particular the removal of the solvent. In addition,
as methods for drying a gel, removal of a solution or a solvent in
a heated, vacuum environment, removal of the solution or the
solvent included in the gel by another solvent, and the like, may
be cited.
[0061] The swelling degree of the gel layer 6 is preferably 110 to
3,000%, and more preferably 150 to 500%. If less than 110%, there
is a risk that sufficient stabilization of the oxido-reduction site
is not carried out due to fewer electrolyte components in the gel,
and in addition, if 3,000% is exceeded, there is a risk that there
are fewer oxido-reduction sites in the gel, which decreases the
electron transport capability; in either case the property of the
photoelectric element decrease.
[0062] Such an organic compound having a redox moiety and a gel
domain within one molecule as described above can be represented by
the following general formula:
(X.sub.i).sub.nj:Y.sub.k
[0063] (X.sub.i).sub.n represents the gel domain and X.sub.i
represents the monomer of the compound forming the gel domain. The
gel domain is formed with a polymer backbone. The polymerization
degree n of the monomer is preferably in the range of n=1 to
100,000. Y represents the redox moiety bonded to (X.sub.i).sub.n.
In addition, j and k are any integers respectively representing the
number of (X.sub.i), and Y contained within one molecule, both
being preferably in the range of 1 to 100. The redox moiety Y may
be bonded to any site on the polymer backbone forming the gel
domain (X.sub.i).sub.n. In addition, the redox moiety Y may contain
a site of a different species, in which case a site with a close
redox potential is desirable from the point of view of electron
exchange reaction.
[0064] As such organic compounds having a redox moiety and a gel
domain within one molecule, polymers having a quinone derivative
backbone comprising chemically bonded quinones, polymers having an
imide derivative backbone containing imide, polymers having a
phenoxyl derivative backbone containing phenoxyl, polymers having a
viologen derivative backbone containing viologen, and the like, may
be cited. In these organic compounds, the respective polymer
backbones are gel domains, and the quinone derivative backbone, the
imide derivative backbone, the phenoxyl derivative backbone and the
viologen derivative backbone are respectively redox moieties.
[0065] Among the organic compounds mentioned above, as examples of
polymers having a quinone derivative backbone comprising chemically
bonded quinones, those having the chemical structures of [Chem. 1]
to [Chem. 4] indicated below may be cited. In [Chem. 1] to [Chem.
4], R represents saturated or unsaturated hydrocarbons such as
methylene, ethylene, propane-1,3-dienyl, ethylidene,
propane-2,2-diyl, alkanediyl, benzylidene, propylene, vinylidene,
propene-1,3-diyl and but-1-en-1,4-diyl; cyclic hydrocarbons such as
cyclohexanediyl, cyclohexenediyl, cyclohexadienediyl, phenylene,
naphthalene and biphenylene; ketos such as oxaryl, malonyl,
succinyl, glutanyl, adipoyl, alkanedioyl, sebacoyl, fumaroyl,
maleoyl, phthaloyl, isophthaloyl and terephthaloyl, divalent acyl
groups; ethers such as oxy, oxymethylenoxy and oxycarbonyl, esters;
groups containing sulfur such as sulfanediyl, sulfanyl and
sulfonyl; groups containing nitrogen such as imino, nitrilo,
hydrazo, azo, azino, diazoamino, urelene and amido; groups
containing silicon such as silane diyl and disilane-1,2-diyl; or
groups comprising these groups substituted or complexed at their
extremities.
[0066] [Chem. 3] is an example of organic compound constituted by
an anthraquinone being chemically bonded to the polymer main-chain.
[Chem. 4] is an example of organic compound constituted by an
anthraquinone being incorporated as a repetitive unit into the
polymer main chain. In addition, [Chem. 5] is an example of organic
compound in which anthraquinone is a crosslinking unit.
Furthermore, [Chem. 6] shows an example of anthraquinone having a
proton-donor group forming an intramolecular hydrogen bond with an
oxygen atom.
##STR00003##
[0067] The quinone polymer described above enables a
high-performance redox reaction that is not rate-limited by proton
movements, and is provided with chemical stability that can endure
long-term use, with no presence of electronic interaction between
quinone groups, which are redox sites (redox moieties). Moreover,
since this quinone polymer does not elute out into the electrolyte
solution, it is useful on the point of being retained in the first
electrode 2 to form the electron transport layer 3.
[0068] In addition, as polymers having an imide derivative backbone
in which the redox moiety Y contains imide, polyimides indicated in
[Chem. 7] and [Chem. 8] can be used. Here, in [Chem. 7] and [Chem.
8], R.sub.1 to R.sub.3 represent aromatic groups such as
1,4-phenylene group and 1,3-phenylene group, or aliphatic chains
such as alkylene group and alkyl ether, and allow the polyimides as
described above to be obtained by heat-imidation. The polyimide
polymer backbone may be crosslinked at the R.sub.1 to R.sub.3
portions, and in addition, may have no crosslinked structure if it
only swells in the used solvent without eluting. If crosslinked,
this portion corresponds to the gel domain. In addition, when
introducing a crosslinked structure is introduced circumstance, an
imide group may be included in the crosslinking unit. If
electrochemically reversible oxido-reduction properties are
exhibited, the imide group may preferably be phthalimide or
pyromellitimide.
##STR00004##
[0069] In addition, as polymers having a phenoxyl derivative
backbone containing phenoxyl, for instance, galvi compounds such as
indicated in [Chem. 9] may be cited. In this galvi compound, the
galvinoxyl group (refer to [Chem. 10]) corresponds to the
oxido-reduction site Y and the polymer backbone corresponds to the
gel domain X.
##STR00005##
[0070] In addition, as polymers having a viologen derivative
backbone containing viologen, polyviologen polymers such as
indicated in [Chem. 11] may be cited.
##STR00006##
[0071] In addition, as polymers having a viologen derivative
backbone containing viologen, viologen compounds such as indicated
in [Chem. 12] and [Chem. 13] may be cited. In these viologen
compounds, [Chem. 14], corresponds to the redox moiety Y and the
polymer backbone corresponds to the gel domains (X.sub.i).sub.n and
(X.sub.i).sub.nj.
##STR00007##
[0072] In [Chem. 3] to [Chem. 13], m and n indicate the
polymerization degree for the monomer, preferably in the range of 1
to 100,000.
[0073] The organic compound having a redox moiety and a polymer
backbone described above forms the gel layer 6 as the polymer
backbone swells by containing an electrolyte solution between the
backbones thereof. By including an electrolyte solution in the
electron transport layer 3 in this way, the ionic state formed by
oxido-reduction reaction of the redox moiety is compensated by
counter ions in the electrolyte solution, allowing the redox moiety
to be stabilized.
[0074] An electrolyte solution containing an electrolyte and a
solvent is sufficient. As electrolytes, support salts and
oxido-reduction system constitutive substances made of an oxidant
and a reductant may be cited, among which, either one or both being
adequate. A support salts (support electrolytes), for instance,
ammonium salts such as tetrabutylammonium perchlorate,
tetraethylammonium hexafluorophosphate, imidazolium salts and
pyridinium salts, alkaline metal salts such as lithium perchlorate
and potassium tetrafluoroborate, and the like, may be cited.
Oxido-reduction system constitutive substances mean substances
existing reversibly in the forms of an oxidant and a reductant in
an oxido-reduction reaction, and as such oxide-reduction system
constitutive substances, for instance, chlorine compound-chlorine,
iodine compound-iodide, bromine-compound-bromine, thallium ion
(III)-thallium ion (I), mercury ion (II)-mercury ion (I), ruthenium
ion (III)-ruthenium ion (II), copper ion (II)-copper ion (I), iron
ion (III)-iron ion (II), nickel ion (II)-nickel ion (III), vanadium
ion (III)-vanadium ion (II), manganate ion-permanganate ion, and
the like, may be cited, with no limitation thereto. In this case,
they function distinctly from the redox moiety within the electron
transport layer 3.
[0075] In addition, as solvents constituting the electrolyte
solution, those containing at least any one among water, organic
solvent and ion liquid may be cited.
[0076] Using water or an organic solvent as a solvent for the
electrolyte solution can stabilize the reduced state of the redox
moiety of the organic compound, allowing electrons to be
transported more stably. While either of aqueous solvents and
organic solvents can be used as the solvent, an organic solvent
having excellent ion conductivity is desirable in order to
stabilize the redox moiety further. As such organic solvents, for
instance, carbonate compounds such as dimethyl carbonate, diethyl
carbonate, methylethyl carbonate, ethylene carbonate and propylene
carbonate, ester compounds such as methyl acetate, methyl
propionate and .gamma.-butyrolactone, ether compounds such as
diethyl ether, 1,2-dimethoxy ethane, 1,3-dioxosilane,
tetrahydrofuran and 2-methyl-tetrahydrofuran, heterocyclic
compounds such as 3-methyl-2-oxazolidinone and 2-methylpyrrolidone,
nitrile compounds such as acetonitrile, methoxy acetonitrile and
propionitrile, aprotic polar compounds such as sulfolane, dimethyl
sulfoxide and dimethyl formamide, and the like, may be cited. These
solvents can each be used alone or two or more species can be mixed
and used in combination. In addition, when the photoelectric
element is formed in particular as a photoelectric conversion
element, from the point of view of improving the solar battery
output properties thereof, the solvent is preferably carbonate
compounds such as ethylene carbonate and propylene carbonate,
heterocyclic compounds such as .gamma.-butyrolactone,
3-methyl-2-oxazolidinone and 2-methylpyrrolidone, nitrile compound
such as acetonitrile, methoxy acetonitrile, propionitrile,
3-methoxy propionitrile and valeric acid nitrile.
[0077] In addition, if an ion liquid is used as the solvent for the
electrolyte solution, the redox moiety-stabilizing action is
particularly improved. Moreover, an ion liquid has excellent
stability since it is not volatile and is highly non-flammable.
Well known ionic liquids can all be used as the ion liquid, for
instance, ionic liquids such as of the imidazolium series, such as
1-ethyl-3-methylimidazolium tetracyanoborate, the pyridine series,
the alicyclic amine series, the aliphatic amine series, the azonium
amine series, and those described in the description of European
patent publication No. 718288, NO 95/18456, Denki Kagaku
(Electrochemistry) Volume 65, No. 11 p. 923 (1997), J. Electrochem.
Soc. Volume 143, No. 10, p. 3099 (1996) and Inorg. Chem. Volume 35,
p. 1168 (1996) can be cited.
[0078] The electron transport layer 3 can be formed by providing on
the surface of the first electrode 2, the gel layer 6 formed with
an organic compound having an electrolyte solution and a redox
moiety such as described above. The electron transport layer 3
refers to a layer in which electrons behave as dopants and, for
instance, refers to a layer having a redox moiety which redox
potential is more noble than +100 mV with respect to a
silver/silver chloride reference electrode.
[0079] From the point of view of maintaining satisfactory electron
transportability, the thickness of the electron transport layer 3
is preferably in the range of 10 nm to 10 mm and particularly
preferably in the range of 100 nm to 100 .mu.m. This thickness
allows both the electron transport property and the interface
surface area of the electron transport layer 3 to be at high
levels.
[0080] In providing the electron transport layer 3 on the surface
of the first electrode 2, while the method of depositing an organic
compound on the surface of first electrode 2, for instance, by a
vacuum process such as sputter method or vapor deposition method,
can be adopted, a wet-type forming method whereby the first
electrode 2 is coated with a solution containing an organic
compound, or the like, is desirable, owing to being a simpler ad
lower-cost preparation method. In particular, when forming the
electron transport layer 3 with a so-called high-molecular weight
organic compound having a number average molecular weight of 1,000
or greater, a wet-type forming method is desirable from the point
of view of formability. As wet-type processes, spincoat method,
drop-cast method obtained by dripping and drying a drop of liquid,
printing methods such as screen printing and gravure printing, and
the like, may be cited.
[0081] The electron transport layer 3 may be formed in such a way
that the redox potential slopes from noble to base in the direction
toward the first electrode 2 in contact with the electron transport
layer 3, that is to say, the value of the redox potential on the
side that is close to the first electrode 2 is more base than the
redox potential on the side that is far from the first electrode 2.
If the redox potential of the electron transport layer 3 slopes
from noble to base in the direction toward the first electrode 2 in
contact with the electron transport layer 3 in this way, this
gradient of redox potential can create a flow of electrons within
the electron transport layer 3, increasing the transportability of
electrons from the electron transport layer 3 to the first
electrode 2 that is in contact with the electron transport layer 3,
allowing the conversion efficiency to be raised further.
[0082] A method for forming the electron transport layer 3 in which
the redox potential has a gradient as described above, for
instance, there is the method whereby, in forming the electron
transport layer 3 using a plurality of organic compounds with
different redox potentials and layering layers of each organic
compound, the organic compounds are combined in such a way that the
redox potential of the organic compound forming the layer on the
side that is close to the first electrode 2 has a higher value than
the redox potential of the organic compound forming the layer on
the side that is far from the first electrode 2. For instance, in
the example of FIG. 2, two layers 31 and 32 are layered to form the
electron transport layer 3, with the species of the organic
compounds forming the layers 31 and 32 being selected so that the
redox potential of the organic compound forming the layer 31 on the
side that is close to the first electrode 2 is base and the redox
potential of the organic compound forming the layer 32 that is far
from the first electrode 2 is noble. Obviously, the electron
transport layer 3 may be formed from a laminate of three or more
layers, in which case, the more a layer is on the side that is
close to the first electrode 2, the more base is the redox
potential set to, sequentially.
[0083] If an imide derivative, a quinone derivative, a viologen
derivative or a phenoxyl derivative is used as the organic compound
for forming the electron transport layer 3 as described above, the
electron transport layer 3 can be formed by combining two or more
species of these organic compounds so that the redox potential
slopes from noble to base in the direction toward the first
electrode 2 in contact with the electron transport layer 3.
[0084] Well known materials can be used as the sensitizing dye of
the present embodiment and, for instance, 9-phenyl xanthene dyes,
coumarin dyes, acridine dyes, triphenyl methane dyes, tetraphenyl
methane dyes, quinone dyes, azo dyes, indigo dyes, cyanine dyes,
merocyanine dyes, xanthene dyes, and the like, may be cited. As
sensitizing dyes, ruthenium-cis-diaqua-bipyridyl complex of the
RuL.sub.2 (H.sub.2O).sub.2 type (where L represents
4,4'-dicarboxyl-2,2'-bipyridine); transition metal complexes of
such types as ruthenium-tris (RuL.sub.3), ruthenium-bis(RuL.sub.2),
osmium-tris (OsL.sub.3) and osmium-bis(OsL.sub.2);
zinc-tetra(4-carboxyphenyl)porphyrin, iron-hexacyanide complex,
phthalocyanine, and the like, may also be cited. In addition, as
sensitizing dye, for instance, dye present in the DSSC chapter of
"Advanced technologies and Material Development of FPD, DSSC,
Optical Memory, and Functional Dye" (N.T.S. Inc.) can also be
applied. In particular, from the point of view of promoting
electric charge separation during photoelectric conversion, dyes
having associative properties are desirable. Dyes forming assembly
and are effective, for instance, dyes indicated by the structural
formula of [Chem. 15] are desirable.
##STR00008##
[0085] In the structural formula, X.sub.1 and X.sub.2 each
independently represents an alkyl group, an alkenyl group, an
aralkyl group, an aryl group, a heterocycle, or an organic group
having at least one or more species of these groups, each being
optionally substituted. Such dyes as [Chem. 15] above are known to
be associating. In this case, the recombination of the electron and
the positive hole present in the electron transport material and
the hole transport material can be reduced dramatically, therefore
conversion efficiency of the photoelectric conversion element can
be improved.
[0086] This sensitizing dye is a sensitizing dye that is present
within the gel layer 6, and in particular, the sensitizing dye is
preferably immobilized within the gel layer 6 by a physical or
chemical action or the like between itself and an organic compound
constituting the gel layer 6.
[0087] "Sensitizing dye is present within the gel layer 6" means
that the sensitizing dye is present not only at the surface layer
of the gel layer 6 but also inside thereof. This allows a state in
which the amount of sensitizing dye present within the gel layer 6
is at a certain value or greater to be maintained continuously,
exerting an output improvement effect for the photoelectric
element. The sensitizing dye is preferably present through the
entirety of the interior of the gel layer 6.
[0088] The "state in which the sensitizing dye is present within
the gel layer 6" includes the "state in which the sensitizing dye
is present in the electrolyte solution constituting the gel layer
6" and the "state in which the sensitizing dye is present in the
gel layer 6 by physically/chemically interacting with an organic
compound constituting the gel layer 6".
[0089] The "state in which the sensitizing dye is retained in the
gel layer 6 by physical interaction with an organic compound
constituting the gel layer 6" includes, for instance, a state in
which an organic compound having a structure that interferes with
the movements of the molecule of sensitizing dye is used as the
organic compound constituting the gel layer 6. As structures that
interfere with the movements of the molecule of sensitizing dye,
structures whereby an organic compound exerts a steric hindrance
through various molecular chains such as an alkyl chain, or,
structures in which the size of the space present between the
molecular chains of the organic compound is reduced to such extent
that movements of the molecule of sensitizing dye can be
suppressed, and the like, may be cited.
[0090] Giving the sensitizing dye an element for the purpose of
exerting physical interactions is also effective. Concretely,
giving the sensitizing dye a structure that exerts steric hindrance
through various molecular chains such as an alkyl chain may be
cited. In addition, bonding two or more sensitizing dyes is also
effective. In order to form a bond between sensitizing dyes it is
effective to utilize saturated hydrocarbons such as methylene,
ethylene, propane-1,3-dienyl, ethylidene, propane-2,2-diyl,
alkanediyl, benzylidene and propylene, unsaturated hydrocarbons
such as vinylidene, propene-1,3-diyl and but-1-en-1,4-diyl, cyclic
hydrocarbons such as cyclohexanediyl, cyclohexenediyl,
cyclohexadienediyl, phenylene, naphthalene and biphenylene, ketos
such as oxaryl, malonyl, succinyl, glutanyl, adipoyl, alkanedioyl,
sebacoyl, fumaroyl, maleoyl, phthaloyl, isophthaloyl and
terephthaloyl, divalent acyl groups, ethers such as oxy,
oxymethylenoxy and oxycarbonyl, esters, groups containing sulfur
such as sulfanediyl, sulfanyl and sulfonyl, groups containing
nitrogen such as imino, nitrilo, hydrazo, azo, azino, diazoamino,
urelene and amido, groups containing silicon such as silanediyl and
disilane-1,2-diyl, or groups comprising these groups substituted or
complexed at their extremities. The above moiety is preferably
bonded to the sensitizing dye via an optionally substituted, linear
or branched alkyl group, for instance methyl, ethyl, i-propyl,
butyl, t-butyl, octyl, 2-ethylhexyl, 2-methoxyethyl, benzyl,
trifluoromethyl, cyanomethyl, ethoxycarbonyl methyl, propoxyethyl,
3-(1-octylpyridinium-4-yl)propyl,
3-(1-butyl-3-methylpyridinium-4-yl)propyl or the like, or an
optionally substituted, linear or branched alkenyl group, for
instance, vinyl, allyl or the like.
[0091] In addition, the "state in which the sensitizing dye is
present in the gel layer 6 by chemical interaction with an organic
compound constituting the gel layer 6" includes a state in which
the sensitizing dye is retained within the gel layer 6, for
instance, by a covalent bond, a coordinate bond, an ionic bond, a
hydrogen bond, a van der Waals bond, or the like, or an
interactions such as a force based on a hydrophobic interaction, a
hydrophilic interaction or an electrostatic interaction, and the
like. In particular, if a sensitizing dye is immobilized within the
gel layer 6 by a chemical interaction between the sensitizing dye
and the organic compound constituting the gel layer 6, the distance
between the sensitizing dye and the organic compound becomes close,
allowing an efficient electron movement to be generated.
[0092] When immobilizing the sensitizing dye within the gel layer 6
by a chemical interaction between the sensitizing dye and the
organic compound, it is desirable to provide a functional group
suitably to the organic compound and the sensitizing dye, and
immobilizing the sensitizing dye with respect to the organic
compound by a chemical reaction or the like mediated by this
functional group. As such functional groups, hydroxyl group,
carboxyl group, phosphate group, sulfo group, nitro group, alkyl
group, carbonate group, aldehyde group, thiol group, and the like,
may be cited. In addition, as reaction forms of the chemical
reaction mediated by this functional group, condensation reaction,
addition reaction, ring-opening reaction, and the like, may be
cited.
[0093] In addition, when chemically bonding the sensitizing dye and
the organic compound constituting the gel layer 6, it is desirable
that the functional group in the sensitizing dye is introduced
close to the site where the electron density becomes higher when
this sensitizing dye is in the light-excited state, and that the
functional group in the organic compound within the gel layer 6 is
introduced close to the site participating to electron transport
within this organic compound. In this case, an improvement in the
efficiency of electron movement from the sensitizing dye to the
organic compound and in the efficiency of electron transport within
the organic compound is intended. In addition, bonding with a
bonding group between the sensitizing dye and the organic compound
constituting the gel layer 6, which has a high electron
transportability that links the electron cloud of the sensitizing
dye and the electron cloud of the organic compound, in particular,
enables efficient electron movement from the sensitizing dye to the
organic compound. Concretely, examples using an ester bond having a
n electron system, or the like, may be cited as a chemical bond
linking the .pi. electron cloud of the sensitizing dye and the .pi.
electron cloud of the organic compound.
[0094] In addition, the timing for bonding the sensitizing dye and
the organic compound may be any among when the organic compound is
in the monomeric state, when the organic compound polymerizes,
after the organic compound has polymerized, when the organic
compound gels and when the organic compound has gelled. As examples
of concrete techniques, the technique of immersing the electron
transport layer 3 formed from the organic compound into a bath
containing the sensitizing dye, the method of coating the first
electrode 2 with a coating solution containing the organic compound
and the sensitizing dye to form a film thereby forming the electron
transport layer 3, and the like, may be cited, and in addition, a
plurality of methods may be combined.
[0095] While the sensitizing dye content within the gel layer 6 is
set suitably, if the sensitizing dye content is 0.1 parts by mass
or greater with respect to 100 parts by mass of the organic
compound in particular, the amount of sensitizing dye per unit
film-thickness of the gel layer 6 becomes sufficiently high,
improving the light absorption capability of the sensitizing dye
and raising the electric current value. In addition, if the
sensitizing dye content is 1,000 parts by mass or less with respect
to 100 parts by mass of the organic compound in particular,
intercalation of an excessive amount of sensitizing dye between the
organic compounds is suppressed, and inhibition by the sensitizing
dye of electron movement within the organic compound is suppressed,
ensuring high electrical conductivity.
[0096] At the same time as the electro-conductive additive 8 is
present within the gel layer 6, at least a portion of this
electro-conductive additive 8 may be in contact with the first
electrode 2. In this case, electron transport property in the
electron transport layer 3 can be improved. This allows the
efficiency of conversion of light and electricity with the
photoelectric element to be improved. That is to say, the reaction
interface is enlarged by having the organic compound and the
electrolyte solution of the electron transport layer 3 form the gel
layer 6, moreover, electron transport property electron transport
layer 3 is improved by the presence of the electro-conductive
additive 8 within the gel layer 6, allowing the efficiency of
light-electricity interconversion by the photoelectric element to
be improved.
[0097] The roughness factor of the electro-conductive additive 8 is
preferably 5 or greater but 2,000 or less. The roughness factor
designates the ratio of the real surface area against the projected
surface area. This projected surface area corresponds to the
projected surface area of the gel layer 6. Regarding the real
surface area, for instance if the electro-conductive additive 8 is
constituted with n spherical electro-conductive materials having a
diameter of r, the real surface area of the electro-conductive
additive 8 is n.times.4.times..pi..times.r.sup.2. When this real
surface area of the electro-conductive additive 8 cannot be
determined from the shape of the electro-conductive additive 8, it
may be determine by the nitrogen adsorption method. In this case,
the electricity-collection effect of the gel layer 6 rises, and at
the same time, the side reaction at the surface of the
electro-conductive additive 8 is suppressed, further improving the
conversion efficiency.
[0098] The electro-conductive additive 8 may be formed of an
aggregation of particles of electro-conductive materials. In this
case, by solely mixing particles of electro-conductive material to
a gel formed from the organic compound and the electrolyte solution
of the electron transport layer 3, electron transport property in
the electron transport layer 3 can be improved, further improving
the conversion efficiency.
[0099] In addition, as another aspect, the electro-conductive
additive 8 may be formed from a fibrous electro-conductive
material. In this case, since the electro-conductive material is
fibrous, reinforcing the strength of the electro-conductive
additive 8 formed from this electro-conductive material to form the
electro-conductive additive 8 with high porosity is facilitated.
Therefore, forming the electron transport layer 3 or the gel layer
6 in the voids of the electro-conductive additive 8 is
facilitated.
[0100] The average external diameter of the fibrous
electro-conductive material is preferably 50 nm or greater but
1,000 nm or less. This average external diameter of
electro-conductive material is the mean value of the external
diameter of the electro-conductive material as measured from the
results of observation by an electron microscope such as SEM
(number of measurements: 30). In this case, the strength of the
electro-conductive additive 8 can be improved further to form an
electro-conductive additive 8 with high porosity, and at the same
time, the specific surface area of the electro-conductive additive
8 can be enlarged sufficiently, further improving the output of the
photoelectric element.
[0101] The porosity of the electro-conductive additive 8 formed
from the fibrous electro-conductive material may be 50% or greater
but 95% or less. In this case, the electron transport property in
the electron transport layer 3 improves further by having a
sufficient amount of electro-conductive additive 8 present within
the gel layer 6. In addition, sufficiently securing a region where
photoelectric conversion is possible within the gel layer 6 becomes
possible by having sufficient amounts of organic compounds and
electrolyte solution in the voids of the electro-conductive
additive 8, further improving the conversion efficiency.
[0102] The average fiber length/average fiber diameter ratio of the
fibrous electro-conductive material is preferably 1,000 or greater.
The average fiber length and the average fiber diameter are the
mean values of the fiber length and the fiber diameter of the
electro-conductive material as measured from the results of
observation by an electron microscope such as SEM (number of
measurements: 30). The node portions of the fibrous
electro-conductive material are excluded from the fiber diameter
measurement locations. In this case, layering the fibrous
electro-conductive materials in a state in which they are arranged
in the direction of the plane of the first electrode 2 is
facilitated, rising the porosity of the electro-conductive additive
8 formed from the fibrous electro-conductive materials, further
improving the conversion efficiency.
[0103] The electro-conductive additive 8 may be present within the
gel layer 6. The electro-conductive additive 8 is used for the
purpose of improving the electron transport property between the
electron transport layer 3 and the first electrode 2. The
electro-conductive additive 8 is preferably in a state where, for
instance, it is mixed within the electron transport layer 3 to be
chained by being in contact with one another at the same time as a
portion is in contact with the first electrode 2. In this case, the
movement of electrons from the electron transport layer 3 to the
first electrode 2 or from the first electrode 2 to the electron
transport layer 3 becomes extremely rapid as it is carried out
through the electro-conductive additive 8, allowing the electron
transport property between the electron transport layer 3 and the
first electrode 2 to be improved further. For instance, when the
photoelectric element is a photoelectric conversion element such as
a dye-sensitized photoelectric conversion element, the
electro-conductive additive 8 can collect electricity efficiently
from the electron transport layer 3 and transport it rapidly to the
first electrode 2.
[0104] The electro-conductive additive 8 present within the gel
layer 6 of the electron transport layer 3 is preferably formed from
a material provided with both light-transmittance and electric
conductivity. Concretely, the electro-conductive material is
preferably present within the electron transport layer 3. ITO
(indium-tin oxide), tin oxide, zinc oxide, silver, gold, copper,
carbon nanotube, graphite and the like are desirable as such
electro-conductive materials. In addition, Pastolan, manufactured
by Mitsui Mining & Smelting Co., Ltd, which has barium sulfate
or aluminum borate as the core and tin oxide, doped tin oxide, ITO,
or the like, coated onto this core may also be cited as the
electro-conductive material. In addition, metal microparticles can
also be used in a range where the electron transport layer 3 does
not loose light-transmittance.
[0105] The volume resistivity of the electro-conductive additive 8
is preferably 10.sup.7 .OMEGA./cm or less, more preferably 10.sup.5
.OMEGA./cm or less, and particularly preferably 10 .OMEGA./cm or
less. At this time, the lower limit value, while not limited in
particular, is in general on the order of 10.sup.-9 .OMEGA./cm.
While not to be of particular concern, the resistivity of the
electro-conductive additive 8 is preferably the same resistivity as
in the first electrode 2.
[0106] The electro-conductive additive 8 may be formed of an
aggregation of a plurality of particles of electro-conductive
materials being chained while coming into contact as shown in FIG.
4(a), and in addition, may be formed from rod-shaped
electro-conductive materials as shown in FIG. 4(b). When the
electro-conductive additive 8 is formed of the aggregation of
particles of electro-conductive materials, the average particle
size of the electro-conductive material thereof is preferably 1 nm
or greater but 1 .mu.m or less. The average particle size is the
mean value of the particle size of the electro-conductive material
as measured from the results of observation by an electron
microscope such as SEM (number of measurements: 30).
[0107] In this case, owing to the average particle size being 1 nm
or greater, the electro-conductive material 3 does not become
isolated in the electron transport layer 3, and in addition, owing
to the average particle size being 1 .mu.m or less, the contact
surface area with the electron transport layer 3 can be rendered
sufficient. Consequently, a sufficient electricity-collection
effect can be obtained.
[0108] From the points of view of taking up a large contact surface
area with the electron transport layer 3 and securing a contact
point with the electro-conductive material 3, a rod-shape is also
desirable for the electro-conductive additive 8. Here, the
rod-shape designates shapes that include, not only those that are
straight shapes, but also those that have, for instance,
fiber-shape, needle-shape or a curved elongated shape. When the
electro-conductive additive 8 is formed from a rod-shaped
electro-conductive material, the average axial ratio thereof
between the long axis and the short axis is preferably 5 or greater
but 50 or less. If the average axial ratio is 5 or greater, a
contact occurs among the electro-conductive materials 3 mixed into
the electron transport layer 3 internal and mutually between the
electro-conductive material 3 and the first electrode 2, allowing
the electrical conduction to become extremely satisfactory, which
can decrease the resistance at the interface between the electron
transport layer 3 and the first electrode 2. In addition, having
the average axial ratio at 50 or less can prevent the
electro-conductive additive 8 from being mechanically destroyed
when the electro-conductive additive 8, the organic compound, and
the like, are mixed uniformly to prepare a paste.
[0109] In addition, then the electro-conductive additive 8 is
formed from a rod-shaped electro-conductive material, the average
external diameter of the short axis of this electro-conductive
material is preferably 1 nm or greater but 20 .mu.m or less. By
having the average external diameter of the short axis of this
electro-conductive material at nm or greater, the
electro-conductive material is not mechanically destroyed when a
paste comprising the electro-conductive material and the organic
compound uniformly mixed is prepared. Therefore, when forming the
electron transport layer 3 from the paste, the resistance at the
interface between the electron transport layer 3 and the first
electrode 2 can be reduced. In addition, by having the average
external diameter of the short axis of this electro-conductive
material at 20 .mu.m or less, the decrease in organic compound per
unit volume in electron transport layer 3, which accompanies the
addition of the electric conductor, can be suppressed.
[0110] In addition, it is particularly desirable that the
electro-conductive additive 8 is formed from fibrous
electro-conductive materials this case, in order to layer the
fibrous electro-conductive materials in a state in which they are
arranged in the direction of the plane of the first electrode 2, by
assuming a structure in which fibers that are arranged in the
direction of the plane of the first electrode 2 are layered
obviously within the plane of the fiber orientation, but also in
the direction of the film-thickness, a high electricity-collection
effect can be realized. In addition, since the electro-conductive
material is fibrous, the strength of the electro-conductive
additive 8 formed from this electro-conductive material becomes
stronger, raising the porosity of the electro-conductive additive 8
is facilitated, and forming the electron transport layer 3 or the
gel layer 6 in the voids of the electro-conductive additive 8 is
facilitated.
[0111] In addition, when the electro-conductive additive 8 is
formed from the fibrous electro-conductive material, the average
external diameter of the short axis of the fibrous
electro-conductive material is preferably 50 nm or greater but
1,000 nm or less. By having the average external diameter at 50 nm
or greater, the strength of the electro-conductive additive 8 is
further improved, allowing an electro-conductive additive 8 with
high porosity to be formed. In addition, when providing the
electro-conductive additive 8 on the first electrode 2, this
facilitates forming first on the first electrode 2 only a highly
strong porous electro-conductive film comprising a fibrous
electro-conductive material to use this porous electro-conductive
film as the electro-conductive additive 8, and then, forming the
electron transport layer 3 or the gel layer 6 in the voids of this
electro-conductive additive 8. In addition, by having the average
external diameter at 1,000 nm or less, the porosity of the
electro-conductive additive 8 formed from the fibrous
electro-conductive material is increased while at the same time the
specific surface area thereof is increased sufficiently, thereby
allowing the output of the photoelectric element to be
increased.
[0112] In addition, the porosity of the electro-conductive additive
8 formed from the fibrous electro-conductive material is preferably
50% or greater but 95% or less. Here, the porosity of the
electro-conductive additive 8 formed from the fibrous
electro-conductive material is the porosity of the layer comprising
the electro-conductive additive 8 only (porous electro-conductive
film); excluding the organic compound, the electrolyte solution,
and the like, from the gel layer 6. Having the porosity at 50% or
greater allows sufficient amounts of organic compound and
electrolyte solution constituting the electron transport layer 3 or
the gel layer 6 to be present within the porous electro-conductive
film, and regions where photoelectric conversion is possible can be
secured sufficiently within the gel layer 6. In addition, having
the porosity at 95% or less prevents the distance from the first
electrode 2 to the fibrous electro-conductive material from
becoming excessively long, which can prevent the resistance-loss
reducing effect from diminishing.
[0113] In addition, the average fiber length/average fiber diameter
ratio (average axial ratio) of the fibrous electro-conductive
material is preferably 1,000 or greater. In this case, layering the
fibrous electro-conductive materials in a state in which they are
arranged in the direction of the plane of the first electrode 2 is
facilitated. FIG. 4 (c) shows schematically how the fibrous
electro-conductive material 9 is layered in a state in which it is
arranged in the planar direction to constitute the
electro-conductive additive 8, and FIG. 5 shows an electron
micrograph in a planar view of the electro-conductive additive 8
constituted with the fibrous electro-conductive material 9.
Therefore, the porosity of the electro-conductive additive 8 formed
from fibrous electro-conductive material becomes higher, allowing a
higher light-electricity interconversion efficiency to be
realized.
[0114] The roughness factor of the electro-conductive additive 8 in
the gel layer 6 is preferably 5 or greater but 2,000 or less. When
this roughness factor is less than 5, there is the risk that the
electron movement distance within the gel layer 6 becomes long,
such that the electricity-collection effect from the gel layer 6 is
not sufficiently obtained. In addition, when the roughness factor
of the electro-conductive additive 8 is greater than 2,000, there
is the risk that the occurrence of a side reaction at the surface
of the electro-conductive additive 8 becomes facilitated, which is
a factor in a decrease in the conversion efficiency. Generally, if
the first electrode 2 is a transparent electrode film formed from
ITO, or the like, this first electrode 2 becomes a non-porous,
compact film, the roughness factor thereof being, in general, a
value of 1.5 or less.
[0115] For the electro-conductive additive 8 such as described
above to be present within the gel layer 6, for instance, the
organic compound and the electro-conductive additive 8 for forming
the electron transport layer 3 are mixed to prepare a mixture such
as a paste, and this mixture is formed into a coating film by
similar methods to the forming of the electron transport layer 3 on
the surface of the first electrode 2 already described. In
addition, coating a solution comprising a pre-dispersed
electro-conductive material on the surface of the first electrode 2
and drying this solution thereby forming the electro-conductive
additive 8 comprising a porous electro-conductive film over the
first electrode 2, and then, coating a solution containing the
organic compound for forming the electron transport layer 3 over
this porous electro-conductive film, is also adequate. In this
case, an electro-conductive material may further be mixed in the
solution containing the organic compound.
[0116] As methods for mixing the organic compound and the
electro-conductive material for forming the electron transport
layer 3, well known general-purpose mixing means may be adopted
(for instance, wheel-form kneader, ball-form kneader, blade-form
kneader, roll-form kneader, mortar, automatic mortar grinder,
colloid mill, omnimixer, swing-mix, electromagnetic mixer and the
like). This allows a mixed paste or slurry of the organic compound
and the electro-conductive material to be obtained.
[0117] In addition, as hole transport materials for forming the
hole transport layer 4, an electrolyte solution comprising
electrolytes such as a redox pair dissolved in a solvent, solid
electrolytes such as molten salts, p-type semiconductors such as
copper iodide, amine derivatives such as triphenyl amine,
electro-conductive polymers such as polyacetylene, polyaniline and
polythiophene, and the like, may be cited.
[0118] When forming the hole transport layer 4 with an electrolyte
solution, the hole transport layer 4 can also be formed with the
electrolyte solution constituting the gel layer 6. In this case,
the electrolyte solution constituting the gel layer 6 constitutes a
portion of the hole transport layer 4.
[0119] In addition, when forming the hole transport layer 4 with an
electrolyte solution, the electrolyte solution may assume a
structure retained in the form of a polymer matrix. As
polyvinylidene fluoride series macromolecular compounds used as the
polymer matrix, homopolymer of vinylidene fluoride, or copolymer of
vinylidene fluoride and another polymerizable monomer, preferably a
radical polymerizable Monomer, may be cited. As the other
polymerizable monomers copolymerizing with vinylidene fluoride
(hereafter referred to as copolymerizable monomer), concretely,
hexafluoropropylene, tetrafluoroethylene, trifluoroethylene,
ethylene, propylene, acrylonitrile, vinylidene chloride, methyl
acrylate, ethyl acrylate, methyl methacrylate, styrene and the
like, can be given as examples.
[0120] The hole transport layer 4 may contain a stable radical
compound. In this case, a positive hole generated by electric
charge separation can be efficiently transported to the
counter-electrode by the extremely rapid electron transfer reaction
of the stable radical compound, which allows the photoelectric
conversion efficiency of the photoelectric element to be
improved.
[0121] While not to be limited in particular as long as they are
compounds having a chemical species having an unpaired electron,
that is to say, a radical, radical compounds having a nitroxide
(NO.) within the molecule are desirable as the stable radical
compounds. In addition, the molecular weight (number average
molecular weight) of the stable radical compound is preferably
1,000 or greater, in which case, since the stable radical compound
is solid or approaches a solid at an ordinary temperature,
volatilization is unlikely to occur, allowing the stability of the
element to be improved.
[0122] This stable radical compound will be described further. The
stable radical compound is a compound that generates a radical
compound through at least one process among an electrochemical
oxidation reaction and an electrochemical reduction reaction. While
the species of the stable radical compound is not limited in
particular, it is preferably a radical compound that is stable. In
particular, the stable radical compound is preferably an organic
compound containing any one or both structural units in [Chem. 16]
and [Chem. 17] below:
##STR00009##
[0123] In the formula, substituent R.sup.1 represents a substituted
or unsubstituted C2-C30 alkylene group, C2-C30 alkenylene group, or
C4-C30 arylene group, X represents an oxy radical group, a nitroxyl
radical group, a sulfur radical group, a hydrazyl radical group, a
carbon radical group, or a boron radical group, and n.sup.1
represents an integer of 2 or greater.
##STR00010##
[0124] In the formula, substituents R.sup.2 and R.sup.3 each
independently represents a substituted or unsubstituted C2-C30
alkylene group, C2-C30 alkenylene group, or C4-C30 arylene group, Y
represents a nitroxyl radical group, a sulfur radical group, a
hydrazyl radical, group, or a carbon radical group, and n.sup.2
represents an integer of 2 or greater.
[0125] As the stable radical compounds indicated in [Chem. 16] and
formula [Chem. 17], for instance, oxy radical compound, nitroxyl
radical compound, carbon radical compound, nitrogen radical
compound, boron radical compound, sulfur radical compound, and the
like, may be cited.
[0126] As concrete examples of the oxy radical compound, for
instance, the following aryloxy radical compounds indicated in
[Chem. 18] to [Chem. 19], the semiquinone radical compounds
indicated in [Chem. 20], and the like, may be cited.
##STR00011##
[0127] In the chemical formulae indicated by [Chem. 18] to [Chem.
20], the substituents R.sup.4 to R.sup.7 each independently
represents a hydrogen atom, a substituted or unsubstituted
aliphatic or aromatic C1-C30 hydrocarbon group, a halogen group, a
hydroxyl group, a nitro group, a nitroso group, a cyano group, an
alkoxy group, an aryloxy group or an acyl group. In the chemical
formula [Chem. 20], n.sup.3 represents an integer of 2 or
greater.
[0128] In addition, as concrete examples of nitroxyl radical
compound, stable radical compounds having the peridinoxy ring
indicated by [Chem. 21], stable radical compounds having the
pyrrolidinoxy ring indicated by [Chem. 22], stable radical
compounds having the pyrrolinone ring indicated by [Chem. 23],
stable radical compounds having the nitronyl nitroxide structure
indicated by [Chem. 24], in the following, and the like, may be
cited.
##STR00012##
[0129] In the chemical formulae indicated by [Chem. 21] to [Chem.
23], R.sup.8 to R.sup.10 and R.sup.A to R.sup.L each independently
represents a hydrogen atom, a substituted or unsubstituted
aliphatic or aromatic C1-C30 hydrocarbon group, a halogen group, a
hydroxyl group, a nitro group, a nitroso group, a cyano group, an
alkoxy group, an aryloxy group or an acyl group. In addition, in
the chemical formula indicated by [Chem. 24], n.sup.4 represents an
integer of 2 or greater.
[0130] In addition, as concrete examples of the nitroxyl radical
compound, radical compounds having the tervalent hydrazyl group
indicated by [Chem. 25], radical compounds having the tervalent
verdazyl group indicated by [Chem. 26], radical compounds having
the amino triazine structure indicated by [Chem. 27], in the
following and the like, may be cited.
##STR00013##
[0131] In chemical formulae [Chem. 25] to [Chem. 27], R.sup.11 to
R.sup.19 each independently represents a hydrogen atom, substituted
or unsubstituted aliphatic or aromatic C1-C30 hydrocarbon group, a
halogen group, a hydroxyl group, a nitro group, a nitroso group, a
cyano group, an alkoxy group, an aryloxy group or an acyl
group.
[0132] Any of the organic macromolecular compounds in [Chem. 16] to
[Chem. 27] above has excellent stability, and as a result, can be
used stably as a photoelectric conversion element or an
energy-accumulating element, allowing a photoelectric element
having excellent stability, and moreover, excellent reaction speed,
to be obtained readily.
[0133] In addition, using a stable radical that is in the solid
state at room temperature is desirable. In this case, the contact
between the radical compound and the electron transport layer 3 can
be maintained stably, allowing alteration and deterioration due to
side reaction or fusion with another chemical compound, or
diffusion, to be suppressed. As a result, the stability of the
photoelectric element can be rendered excellent.
[0134] The electric charge transport layer (hole transport layer 4)
may contain the azaadamantane-N-oxyl derivative indicated in [Chem.
28]. In this case, when the electron transport layer 3 is radiated
by light, an electron or a positive hole is generated from the
electron transport layer 3, this electron or positive hole
participates in the oxido-reduction reaction of the
azaadamantane-N-oxyl derivative, the azaadamantane-N-oxyl
derivative becomes a redox couple accompanying the electrochemical
oxidation reaction or reduction reaction, at which time the
electric current is taken outside, with the first electrode 2
serving as the negative electrode and the second electrode 5
serving as the positive electrode.
##STR00014##
[0135] R.sub.1 and R.sub.2 each independently represents hydrogen,
fluorine, an alkyl group or a substituted alkyl group, and X.sub.1
represents a methylene group or the N-oxyl group indicated in
[Chem. 29].
##STR00015##
[0136] The azaadamantane-N-oxyl derivative contains a nitroxide
(NO.) in the molecule, and generates a radical compound in at least
one process of electrochemical oxidation reaction or reduction
reaction. The generation this radical compound allows the electric
charge to be transported to the counter-electrode efficiently by an
extremely rapid charge-transfer reaction. Furthermore the
azaadamantane-N-oxyl derivative is a highly active compound as an
oxidation catalyst for alcohols, with a catalytic capability
exceeding that of the 2,2,6,6-tetramethyl piperidine-1-oxyl (TEMPO)
derivative. Therefore, it is anticipated that the electron
donating-accepting reaction at the joining interface between the
electric charge transport layer (hole transport layer 4) and the
photosensitizer is rapid, rectification property of the generated
electron provided at the electric charge separation interface, and
electric charge recombination after electric charge separation is
suppressed. In addition, due to the azaadamantane-N-oxyl derivative
having a nitroxide, the sites that trap the electric charges become
small, which allows the portion that can transport the electric
charge to have high density, improving the electric charge
transport properties, thereby allowing the photoelectric conversion
efficiency of the element to be improved.
[0137] The azaadamantane-N-oxyl derivative is preferably one or
more species selected from the azaadamantane-N-oxyl indicated in
[Chem. 30] and the 1-methyl-2-azaadamantane-N-oxyl indicated in
[Chem. 31]. In this case, as the electric charge transport property
improves further, the photoelectric conversion efficiency of the
element improves.
##STR00016##
[0138] From the point of view of light absorption and
charge-transfer to the semiconductor 1, it is important to control
the redox potential of the azaadamantane-N-oxyl derivative. For
instance, the redox potential can be changed by having a derivative
in which, with respect to the azaadamantane-N-oxyl from [Chem. 28]
in which R.sub.1 and R.sub.2 are both hydrogens, at least one among
R.sub.1 and R.sub.2 has been replaced by a substituted alkyl group
having a substituent such as a hydroxyl group, an ether group, a
carboxyl group, an ester group, a phosphonyl group or a sulfonyl
group.
[0139] In addition, for instance [Chem. 32] indicates a compound
from [Chem. 28] in which both R.sub.1 and R.sub.2 are hydrogens and
X.sub.1 is the N-oxyl group indicated in [Chem. 29] and by having a
plurality of nitroxy radical structures present within a compound
in this way, it can be anticipated that, in addition to being able
to control the redox potential similarly to above, the stability of
the charge-transfer is improved due to an increase in the reaction
sites.
##STR00017##
[0140] In addition, raising the chemical stability of
azaadamantane-N-oxyl derivative is also desirable, for instance, by
fluorine substitution of one or both among R.sub.1 and R.sub.2 in
[Chem. 28], as shown respectively in [Chem. 33] and [Chem. 34].
[Chem. 33] and [Chem. 34] indicate cases where X.sub.1 is a
methylene group.
##STR00018##
[0141] The concentration in the azaadamantane-N-oxyl derivative in
the electric charge transport layer (hole transport layer 4) is
preferably 1 mM to 1 M. If within this range, the
azaadamantane-N-oxyl derivative can exert an electric charge
transfer property that is sufficient for photoelectric conversion.
If the concentration in azaadamantane-N-oxyl derivative is smaller
than 1 mM, there is the risk that the photosensitized electric
charge cannot be transported sufficiently to the
counter-electrode.
[0142] In addition, the second electrode 5 functions as the
positive electrode of the photoelectric element and can be formed
similarly to the first electrode 2 described above. In order to act
efficiently as a positive electrode of the photoelectric element,
this second electrode 5 is preferably formed from a material having
a catalytic action that provides an electron to the reductant of
the electrolyte used for the electric charge transport layer (hole
transport layer 4). As counter-electrode materials for forming the
second electrode 5, although they depend on the species of the
element to be fabricated, for instance, metals such as platinum,
gold, silver, copper, aluminum, rhodium and indium, carbon
materials such as graphite, carbon nanotube and platinum-supporting
carbon, electro-conductive metal oxides such as indium-tin complex
oxide, tin oxide doped with antimony and tin oxide doped with
fluorine, electro-conductive polymers such as polyethylene
dioxythiophene, polypyrrole and polyaniline, and the like, may be
cited. Among these, platinum, graphite, polyethylene dioxythiophene
and the like are particularly desirable.
[0143] The second electrode 5 may be layered and provided above the
second substrate 7, as shown in FIGS. 2 and 3. The second substrate
7 is formed for instance from the same material as the first
substrate 1. If the first substrate 1 has light-transmittance, the
second substrate 7 may have or may not have light-transmittance.
However, in order for injection of light to be possible from both
the first substrate 1 and the second substrate 7, it is desirable
that the second substrate 7 has light-transmittance. If the first
substrate 1 does not have light-transmittance, it is desirable that
the second substrate 7 has light-transmittance. If the second
electrode 5 is to function as a substrate for light injection, the
first substrate 1 may be formed from a material that does not
transmit light.
[0144] When fabricating a photoelectric element, for instance, the
organic compound is layered by a wet-type method, or the like, over
the first electrode 2 provided on the first substrate 1 thereby
forming the electron transport layer 3 fixedly on the first
electrode 2, and the hole transport layer 4 and the second
electrode 5 are layered over this electron transport layer 3. When
forming the hole transport layer 4 with an electrolyte solution,
the hole transport layer 4 can be formed, for instance, by filling
the opening or gap between the electron transport layer 3 and the
second electrode 5 with the electrolyte solution in a sealed state
with a sealant between the electron transport layer 3 and the
second electrode 5. At this time, a portion of the electrolyte
solution penetrates into the electron transport layer 3 while the
organic compound constituting the electron transport layer 3
swells, thereby forming the gel layer 6.
[0145] The photoelectric element constituted as per the above the
description functions as a photoelectric conversion element.
Meeting this photoelectric conversion element, light radiates from
the first substrate 1 side through the first electrode 2, a
sensitizing dye becomes excited by absorbing the light, generated
excitation electrons flow into the electron transport layer 3 and
are taken outside through the first electrode 2 at the same time as
positive holes in the sensitizing dye are taken outside from the
hole transport layer 4 through the second electrode 5.
[0146] The photoelectric element according to the present
embodiment has high storage capability. That is to say, the
open-circuit voltage maintenance rate when light is radiated on the
photoelectric element and then this light to the photoelectric
element is shielded, is high. If light at 200 lux has been radiated
for 300 seconds onto the photoelectric element, at which time point
the open-circuit voltage of the photoelectric element is A (V), and
if the light radiation to the photoelectric element was shielded at
the above time point and this state has been maintained for 5
minutes, at which time point the open-circuit voltage of the
photoelectric element is B (V), then, the open-circuit voltage
maintenance rate is represented by percentage of B with respect to
A ((B/A).times.100(%)). In the photoelectric element according to
the present embodiment, the open-circuit voltage maintenance rate
can be 10% or greater. That is to say, A and B described above can
satisfy the following relational expression:
(B/A).times.100.gtoreq.10.
[0147] It is assumed that this is due to the suppression of the
movements to the mediators (the hole transport materials forming
the hole transport layer 4), of the electrons retained in the
electron transport layer 3 in the present embodiment. When a
photoelectric element having such high storage ability is used as a
power source, destabilization of the supply of power by the
presence and absence of light radiation is suppressed.
EXAMPLES
[0148] Hereafter, the present invention will be described
concretely by way of examples.
[0149] In Examples 9 to 13, the roughness factor of the
electro-conductive additive 8 was determined with the surface area
of the electro-conductive material determined by the nitrogen
adsorption method as the real surface area of the
electro-conductive additive 8 and the projected surface area of the
porous electro-conductive film formed from this electro-conductive
material as the projected surface area of the electro-conductive
additive 8 according to the formula: (real surface area/projected
surface area).times.100=roughness factor.
[0150] In addition, the void volume in the porous
electro-conductive film was determined by the pore distribution
measurement method to determine porosity according to the formula:
(void volume/apparent volume of the porous electro-conductive
film).times.100=porosity.
Example 1
Synthesis of Galvi Monomer
[0151] Into a reaction container, 4-bromo-2,6-di-tert-butyl phenol
(135.8 g; 0.476 mol) and acetonitrile (270 ml) were introduced,
furthermore, under inert atmosphere, N,O-bis
(trimethylsilyl)acetamide (BSA) (106.3 g; 129.6 ml) was added,
which were stirred overnight at 70.degree. C. and reacted until
crystals were deposited completely. The deposited white crystals
were filtered, vacuum-dried and then re-crystallized with ethanol
for purification to obtain a white plate crystal of
(4-bromo-2,6-di-tert-butyl phenoxy)trimethylsilane (150.0 g; 0.420
mol) indicated by the symbol "1" in [Chem. 35].
[0152] Next, in the reaction container, under inert atmosphere, the
above (4-bromo-2,6-di-tert-butyl phenoxy)trimethylsilane (9.83 g;
0.0275 mol) was dissolved in tetrahydrofuran (200 ml), and the
prepared solution was cooled to -78.degree. C. using dry
ice/methanol. Added to this solution inside the reaction container
was 1.58 M of n-butyl lithium/hexane solution (15.8 ml; 0.025 mol),
and lithiation was carried out by stirring at a temperature of
78.degree. C. for 30 minutes. Thereafter, a tetrahydrofuran (75 ml)
solution of methyl 4-bromobenzoate (1.08 g; 0.005 mol, Mw: 215.0,
TCI) was added to this solution, which was then stirred overnight
at -78.degree. C. to room temperature. This changed the solution
from yellow to pale yellow, and to dark blue, which indicates the
generation of anions. After the reaction, an aqueous solution
saturated with ammonium chloride was added to the solution inside
the reaction container until the color of the solution became
completely yellow, and then, this solution was fractionated and
extracted with ether/water to obtain a product in a yellow viscous
liquid form.
[0153] Next, the product, THF (10 ml), methanol (7.5 ml) and a
stirring bar were introduced into a reaction container, after
dissolution, 10 N--HCl (1 to 2 ml) was added gradually until the
solution inside the reaction container changed to red-orange, which
was stirred for 30 minutes at room temperature. Next, by
purification through each of the operations of solvent extraction,
fractionation and extraction by ether/water, solvent extraction,
fractionation by column chromatography (hexane/chloroform=1/1) and
recrystallization with hexane, an orange crystal of
(p-bromophenyl)hydrogalvinoxyl (2.86 g; 0.0049 mol) indicated by
the symbol "2" in [Chem. 35] was obtained.
[0154] Next, inside the reaction container, the above
(p-bromophenyl)hydrogaivinoxyl (2.50 g; 4.33 mmol) was dissolved
under inert atmosphere in toluene (21.6 ml; 0.2 M),
2,6-di-tert-butyl-p-cresol, (4.76 mg; 0.0216 mmol),
tetrakis(triphenylphosphine)palladium (0) (0.150 g; 0.130 mmol),
and tri-n-butylvinyl tin (1.65 g; 5.20 mmol, Mw: 317.1, TCI) were
added rapidly to this solution, which was stirred at 100.degree. C.
for 17 hours.
[0155] The reaction product obtained by this was fractionated and
extracted with ether/water, solvent-extracted, then, fractionated
by flash column chromatography (hexane/chloroform=1/3) and further
purified by recrystallization with hexane to obtain an orange fine
crystal of p-hydrogalvinoxyl styrene (1.54 g; 2.93 mmol) indicated
by the symbol "3" in [Chem. 35].
[0156] (Polymerization of the Galvi Monomer)
[0157] Obtained in the synthesis of galvi monomer above, 1 g of
galvi monomer (p-hydrogalvinoxyl styrene), 57.7 mg of
tetraethyleneglycol diacrylate, and 15.1 mg of
azobisisobutyronitrile were dissolved in 2 ml of tetrahydrofuran,
then, by nitrogen-exchanging and refluxing overnight, the galvi
monomer was polymerized to obtain the galvi polymer indicated by
symbol "4" in [Chem. 35].
[0158] (Formation of the Electron Transport Layer)
[0159] An electro-conductive glass substrate having a thickness of
0.7 mm and a sheet resistance of 100.OMEGA./.quadrature. was
readied as a first substrate 1 provided with a first electrode 2.
This electro-conductive glass substrate was formed from a glass
substrate and a coating film comprising fluorine-doped SnO.sub.2
layered on one side of this glass substrate, the glass substrate
being the first substrate 1 and the coating film being the first
electrode 2.
[0160] The above galvi polymer indicated by the symbol "4" was
dissolved in chlorobenzene at a proportion of 2% by mass. This
solution was spincoated at 2,000 rpm over the first electrode 2 of
the electro-conductive glass substrate and dried under 60.degree.
C. and 0.01 MPa for one hour thereby forming an electron transport
layer 3 having a thickness of 60 nm.
[0161] This electron transport layer 3 was immersed for one hour in
a saturated acetonitrile solution of the sensitizing dye (D131)
indicated by [Chem. 36].
##STR00019## ##STR00020##
[0162] (Fabrication of Element)
[0163] An electro-conductive glass substrate having the same
constitution as the electro-conductive glass substrate in the
formation of the above electron transport layer 3 was readied.
[0164] In chloroplatinic acid, isopropyl alcohol was dissolved so
that the concentration thereof was 5 mM, the obtained solution was
spincoated over the coating film of the electro-conductive glass
substrate and then fired at 400.degree. C. for 30 minutes to form a
second electrode 5.
[0165] Next, the electro-conductive glass substrate provided with
the electron transport layer 3 and the electro-conductive glass
substrate provided with the second electrode 5 were disposed in
such a way that the electron transport layer 3 and the second
electrode 5 were facing one another while at the same time, a 1
mm-wide, 50 .mu.m-thick heat-melting adhesive ("Bynel" manufactured
by Du pont-Mitsui polychemicals Co., Ltd.) was intercalated between
the two parties at the outer edges. By pressing the two
electro-conductive glass substrates in the thickness direction
while heating this heat-melting adhesive, the two
electro-conductive glass substrates were bonded through the
heat-melting adhesive. A gap or opening to serve as the
electrolytic solution injection port was formed in the heat-melting
adhesive. Next, an electrolytic solution was filled from the
injection port between the electron transport layer 3 and the
second electrode 5. Next, the injection port was coated with a
UV-curing resin, then, UV light was radiated to solidify the
UV-curing resin, whereby the injection port was plugged. In this
way, a hole transport layer 4 comprising the electrolytic solution
was formed while at the same time, this electrolytic solution
penetrated into the electron transport layer 3, swelling the
organic compound (galvi polymer) constituting the electron
transport layer 3 and forming the gel layer 6. As the electrolytic
solution, an acetonitrile solution containing 2,2,6,6-tetramethyl
piperidine-1-oxyl at a concentration of 1 M, the sensitizing dye
(D131) at 2 mM, LiTFSI at 0.5 M and N-methyl benzimidazole at 1.6 M
was used. Thus was prepared a photoelectric element.
Example 2
[0166] In Example 1, when forming the electron transport layer 3,
0.2 g of galvi polymer and 0.01 g of sensitizing dye (D131) were
dissolved in 10 ml of chlorobenzene to prepare a coating solution.
This solution was spincoated at 2,000 rpm over the first electrode
2 of an electro-conductive glass substrate and dried under
60.degree. C. and 0.01 MPa for one hour thereby forming an electron
transport layer 3 having a thickness of 60 nm. Immersion of this
electron transport layer 3 into a saturated acetonitrile solution
of sensitizing dye was not carried out.
[0167] A photoelectric element was prepared in a similar manner to
Example 1 except for this.
Example 3
[0168] In Example 1, after the electron transport layer 3 was
formed, this electron transport layer 3 was immersed in an aqueous
solution of tetrabutyl ammonium at a concentration of 0.1 M for 15
minutes thereby anionizing the galvi polymer constituting the
electron transport layer 3. This electron transport layer 3 was
washed with water and then immersed in an aqueous solution of
polydecylviologen (ph 10) at a concentration of 0.1 M for 15
minutes thereby bonding the polydecylviologen electrostatically to
the anionized galvi polymer.
[0169] Next, this electron transport layer 3 was immersed in an
acetonitrile solution containing the sensitizing dye (D131) at a
concentration of 0.3 mM for one hour and then washed with water. In
this way, the sensitizing dye was electrostatically bonded to the
portion derived from polydecylviologen, which is a substance that
is positively charged in the electron transport layer 3.
[0170] In addition, as the electrolytic solution, an acetonitrile
solution containing 2,2,6,6-tetramethyl piperidine-1-oxyl at a
concentration of 1 M, LiTFSI at 0.5 M and N-methyl benzimidazole at
1.6 M was used.
[0171] Otherwise, a photoelectric element was prepared in a similar
manner to Example 1.
Example 4
[0172] The galvi polymer indicated by symbol "4" in [Chem. 35] was
obtained similarly to Example 1 by the procedure of the reaction
indicated in [Chem. 35].
[0173] An electro-conductive glass substrate having a thickness of
0.7 mm and a sheet resistance of 100.OMEGA./.quadrature. was
readied as the first substrate 1 provided with the first electrode
2. This electro-conductive glass substrate was formed from a glass
substrate and a coating film comprising fluorine-doped SnO.sub.2
layered on one of the sides of this glass substrate, the glass
substrate being the first substrate 1 and the coating film being
the first electrode 2.
[0174] The galvi polymer obtained by polymerizing as described
above was dissolved in chlorobenzene at a proportion of 2% by mass,
this galvi polymer solution was spincoated at 2,000 rpm over the
first electrode 2 of the electro-conductive glass substrate and
dried under 60.degree. C. and 0.01 MPa for one hour thereby forming
a layer 31 having a thickness of 60 nm.
[0175] After the layer 31 of galvi polymer was formed in this way,
this layer 31 was immersed in an aqueous solution of tetrabutyl
ammonium at a concentration of 0.1 M for 15 minutes thereby anion
zing the galvi polymer constituting the layer 31. This layer 31 of
galvi polymer was washed with water, then, this layer 31 was
immersed in an aqueous solution of polydecylviologen (pH 10) at a
concentration of 0.1 M for 15 minutes thereby bonding the
polydecylviologen electrostatically to the anionized galvi polymer,
forming a layer 32. In this way, an electron transport layer 3
comprising the layer 31 of galvi polymer and the layer 32 of
polydecylviologen was formed. When the redox potential was measured
for each of the layers 31 and 32 of this electron transport layer 3
by the method indicated below, the redox potential of the layer 31
was 0 V and the redox potential of the layer 32 was -0.4 V, such
that the redox potential of the electron transport layer 3 sloped
from noble to base in the direction toward the first electrode
2.
[0176] Otherwise, a photoelectric element having such a layer
constitution as FIG. 2 was prepared in a similar manner to Example
1.
Example 5
Synthesis of Quinone Polymer
[0177] As quinone polymer, the already-described
poly(1-methacrylamide anthraquinone) of [Chem. 6] was synthesized
by the reaction indicated in [Chem. 37].
##STR00021##
[0178] First, under argon atmosphere, a 10 ml recovery flask was
loaded with 50 mg of 1-methacrylamide anthraquinone (0.172 mmol, 1
eq), 25 .mu.l of divinylbenzene (0.172 mmol, 1 eq), 0.48 g of AIBN
(azobisisobutylonitrile) (3.43 .mu.mol, 0.02 eq), these were
dissolved in 1.72 ml of THF, then, oxygen dissolved in the solvent
was extracted with argon. Next, this solution was degassed and then
reacted at 70.degree. C. for 48 hours. After the end of the
reaction, a precipitate was generated in the solution using
methanol, further Soxhlet-washed with THF, to obtain a 37.3 mg of
polymer in a yellow solid state.
[0179] (Formation of Electron Transport Layer)
[0180] In a similar manner to Example 3, a layer 31 of galvi
polymer was formed over the first electrode 2 of an
electro-conductive glass substrate. Next, a solution comprising 10
mg of the above polymer dissolved in 0.1 g N methyl pyrrolidone was
spincoated at 1,000 rpm over the layer 31 of galvi polymer to form
a 100 nm-thick layer 32 of quinone polymer, forming an electron
transport layer 3 comprising the layer 31 of galvi polymer and the
layer 32 of quinone polymer. When the redox potential was measured
for each of the layers 31 and 32 of this electron transport layer 3
by the method indicated below, the redox potential the layer 31 was
0 V and the redox potential of the layer 32 was -0.8 V, such that
the redox potential of the electron transport layer 3 sloped from
noble to base in the direction toward the first electrode 2.
[0181] Next, this electron transport layer 3 was immersed in an
acetonitrile solution containing the already-described sensitizing
dye (D131) of [Chem. 36] at a concentration of 0.3 mM for one hour,
then washed with water to provide the electron transport layer 3
with the sensitizing dye.
[0182] An electron transport layer 3 was formed in this way, and a
photoelectric element having such a layer constitution as FIG. 2
was prepared in a similar manner to Example 4 for the
remainder.
Example 6
Synthesis of Polyimide
[0183] Under argon atmosphere, added to a 30 ml recovery flask were
310.20 mg (0.001 mol) of 4-4'-oxydiphthalic anhydride, 2 ml of
N--N-dimethyl acetamide and 108.15 mg (0.001 mol) of 1,4-phenylene
diamine, which were reacted under room temperature for 18 hours.
After the end of the reaction, purified by precipitation in
acetone, 411.8 mg of polymer indicated in [Chem. 38] was obtained
as a white solid.
##STR00022##
[0184] (Formation of Electron Transport Layer)
[0185] In a similar manner to Example 4, a layer 31 of galvi
polymer was formed over the first electrode 2 of an
electro-conductive glass substrate. Next, a solution in which 5.47
mg of the above polymer and 0.1 g of N-methyl pyrrolidone were
mixed was prepared, and this solution was spincoated at 1,000 rpm
on the surface of the layer 31 of galvi polymer to form a film,
which thickness was 100 nm. This was heated stepwise at 150.degree.
C., 180.degree. C., 200.degree. C. and 220.degree. C. for 20
minutes each, and at 250.degree. C. for 30 minutes, to be imidized
as indicated in [Chem. 39] and form a layer 32 of polyimide,
forming an electron transport layer 3 comprising the layer 31 of
galvi polymer and the layer 32 of polyimide. When the redox
potential was measured for each of the layers 31 and 32 of this
electron transport layer 3 by the method indicated below, the redox
potential of the layer 31 was 0 V and the redox potential of the
layer 32 was -1.0 V, such that the redox potential of the electron
transport layer 3 sloped from noble to base in the direction toward
the first electrode 2.
##STR00023##
[0186] Next, this electron transport layer 3 was immersed in an
acetonitrile solution containing the already-described sensitizing
dye (D131) of [Chem. 36] at a concentration of 0.3 mM for one hour
and then washed with water to provide the electron transport layer
3 with the sensitizing dye.
[0187] An electron transport layer 3 was formed in this way, and a
photoelectric element having such a layer constitution as FIG. 2
was prepared in a similar manner to Example 4 for the
remainder.
Example 7
[0188] The galvi polymer indicated by symbol "4" in [Chem. 35] was
obtained similarly to Example 1 by the procedure of the reaction
indicated in [Chem. 35].
[0189] A first substrate 1 made of 1 mm-thick glass on the surface
of which the first electrode 2 was formed with a transparent
electro-conductive oxide of fluorine-doped SnO.sub.2 (manufactured
by Asahi Glass Co., Ltd., 10.OMEGA./.quadrature.) was used.
[0190] Synthesized as described above, 22.5 mg of galvi compound
(galvi polymer) was dissolved in 4.5 ml of chloroform, which was
drop-cast on the surface of the first electrode 2 to be formed into
a film having a film-thickness of 100 nm.
[0191] Next, the first electrode 2 was electrified to apply a
voltage of 1.5 V or lower, whereby the galvi compound was
electrolytically oxidized and derived into a radical, forming a
semiconductor by means of the galvinoxy radical polymer (the
electron transport layer 3) on the surface of the first electrode
2.
[0192] That which was formed by layering the semiconductor (the
electron transport layer 3) on the first electrode 2 in this way
was used as the working electrode, a platinum-wire electrode as the
counter-electrode, a silver/silver chloride electrode as the
reference electrode, and lithium perchlorate as the support
electrolyte solution, which were set on an electrochemical
measurement bath. Then, when measurements were carried out by
cyclic voltammetry, a stable and reversible oxido-reduction wave
derived from the galvinoxy radical at 0 V with respect to the
reference electrode was measured, confirming the operation as an
n-type semiconductor. In addition, the amount of electrons in the
electrode reaction of the reduction process agreed approximately
with the theoretical reaction amount calculated from the number of
radical sites (calculated from the amount of coating), such that a
quantitative reaction of the coated galvinoxy radical was observed.
In addition, even when the voltage was applied repeatedly (40
cycles) the oxido-reduction wave was observed stably, such that a
stable operation was confirmed.
[0193] Next, the semiconductor (the electron transport layer 3)
formed in this way was modified to carry a photosensitizer 5 by
spincoating a saturated acetonitrile solution of the 0131 dye.
[0194] Then, the semiconductor (the electron transport layer 3) was
scraped over the periphery of the first electrode 2, and a sealant
comprising a heat-melting adhesive ("Bynel" manufactured by Du
pont-Mitsui polychemicals Co., Ltd.) was disposed over the first
electrode 2 so as to surround the semiconductor (the electron
transport layer 3). Next, the second electrode 5 comprising Pt was
bonded opposite to the first electrode 2 having a hole near the
center opened with a diamond drill. An electrolyte solution
prepared by dissolving respectively 5 mol/l of D131 dye, 0.1 mol/l
of azaadamantane-N-oxyl, 1.6 mol/l of N-methyl benzimidazole, and 1
mol/l lithium perchlorate in acetonitrile was injected from the
hole, and the hole was sealed with a UV-curing resin to obtain a
photoelectric element.
Example 8
[0195] In Example 7, instead of azaadamantane-N-oxyl,
2,2,6,6-tetramethyl piperidine-1-oxyl (TEMPO) was used to prepare a
photoelectric element.
Example 9
[0196] The galvi polymer indicated by symbol "4" in [Chem. 35] was
obtained similarly to Example 1 by the procedure of the reaction
indicated in [Chem. 35].
[0197] An electro-conductive glass substrate having a thickness of
0.7 mm and a sheet resistance of 100.OMEGA./.quadrature. was
readied as the first substrate 1 provided with the first electrode
2. This electro-conductive glass substrate was formed from a glass
substrate and a coating film comprising fluorine-doped SnO.sub.2
layered on one side of this glass substrate, the glass substrate
being the first substrate 1 and the coating film being the first
electrode 2. The roughness factor of the coating film was 1.5.
[0198] Dissolved and dispersed into chlorobenzene were 2% by mass
of galvi polymer (symbol "4" in [Chem. 35]) and 1% by mass of ITO
particles (20 nm.phi.)). This solution was spincoated at 1,000 rpm
over the first electrode 2 of the electro-conductive glass
substrate and dried under 60.degree. C. and 0.01 MPa for one hour
thereby forming simultaneously an electro-conductive additive 8 and
an electron transport layer 3 comprising connected bodies of ITO
particles. The thickness of this electro-conductive additive 8 and
electron transport layer 3 was 120 nm. The roughness factor of the
electro-conductive additive 8 was 110 and the porosity was 40%.
[0199] This electron transport layer 3 was immersed for one hour in
a saturated acetonitrile solution of the sensitizing dye (D131)
indicated by [Chem. 36].
[0200] A photoelectric element was prepared in a similar manner to
Example 1 for the conditions other than this.
Example 10
[0201] In Example 9, when preparing the electro-conductive additive
8 and the electron transport layer 3, instead of the ITO particles,
a solution comprising a rod-shaped (fibrous) electro-conductive
material (manufactured by Mitsui Mining & Smelting Co., Ltd,
TYPE-V; average axial ratio: 8.0; average short axis diameter: 1
.mu.m) dispersed at a concentration of approximately 5% by mass was
prepared and used. Otherwise, a photoelectric element was prepared
in a similar manner to Example 9. In the above, the roughness
factor of the electro-conductive additive 8 comprising the
rod-shaped (fibrous) electro-conductive material was 150 and the
porosity was 60%.
Example 11
[0202] When forming the electron transport layer 3, first, into a
terpineol solution containing 20% by mass of ethyl cellulose, tin
oxide (average particle size: 20 nm) was dispersed so that the
concentration thereof was 20% by mass to prepare a tin oxide paste.
This tin oxide paste was coated onto an electro-conductive glass
substrate having the same constitution as Example 9 and fired at
450.degree. C. for 30 minutes to prepare an electro-conductive
additive 8 comprising a 3 .mu.m-thick porous electro-conductive
film. The roughness factor of this electro-conductive additive 8
was 500 and the porosity was 40%.
[0203] Next, a solution comprising the galvi polymer indicated in
Example 9 (symbol "4" in [Chem. 35]) dissolved in chlorobenzene so
that the concentration thereof was 2% by mass was prepared. This
solution was spincoated at 500 rpm on the porous electro-conductive
film and dried under 60.degree. C. and 0.01 MPa for one hour to
form an electron transport layer 3. This electron transport layer 3
was immersed in a saturated acetonitrile solution of the
sensitizing dye (D131) indicated by [Chem. 36] for one hour.
[0204] Otherwise, a photoelectric element was prepared in a similar
manner to Example 9.
Example 12
[0205] By a similar technique to the case of Example 11 when
forming the electro-conductive additive 8, an electro-conductive
additive 8 comprising a 10 .mu.m-thick porous electro-conductive
film. The roughness factor of this electro-conductive additive 8
was 2,000 and the porosity was 40%.
[0206] Next, using a solution comprising 2% by mass of galvi
polymer (symbol "4" in [Chem. 35]) dissolved in chlorobenzene,
electron transport layer 3 was formed by a similar technique to the
case of Example 11.
[0207] Otherwise, a photoelectric element was prepared in a similar
manner to Example 11.
Example 13
[0208] When forming the electron transport layer 3, first, a
dimethyl formamide solution of polyvinyl acetate (molecular weight:
500,000) at a concentration of 14% by mass was prepared, which was
designated the A solution. In addition, 13.5 g of tin chloride
hydrate was dissolved in 100 ml of ethanol and refluxed for 3 hours
to be turned into a tin oxide solution, which was designated the B
solution. Then, the A solution and the B solution were mixed at a
mass ratio of 0.8:1 and stirred for 6 hours, and the obtained
solution was designated the C solution. This C solution was coated
over a transparent electrode of an electro-conductive glass
substrate by the electro-spinning method and fired at 450.degree.
C. for 30 minutes. In this way, an electro-conductive additive 8
comprising a .mu.m-thick porous electro-conductive film formed from
fibrous electro-conductive material with an average external
diameter (short axis diameter) of 100 nm. A electron micrograph in
a planar view of this porous electro-conductive film is shown in
FIG. 5. The roughness factor of this electro-conductive additive 8
was 200 and the porosity was 80%.
[0209] Next, a solution comprising 2% by mass of the galvi polymer
in Example 9 (symbol "4" in [Chem. 35]) dissolved in chlorobenzene
was prepared. This solution was spincoated at 500 rpm on the porous
electro-conductive film and dried under 60.degree. C. and 0.01 MPa
for one hour to form an electron transport layer 3.
[0210] This electron transport layer 3 was immersed in a saturated
acetonitrile solution of the sensitizing dye (D131) indicated by
[Chem. 36] for one hour.
[0211] Otherwise, a photoelectric element was prepared in a Similar
manner to Example 9.
Comparative Example 1
[0212] In Example 1, after the electron transport layer 3 was
formed, saturated acetonitrile solution of the sensitizing dye
(D131) was spincoated on the surface of this electron transport
layer 3 spincoat to attach the sensitizing dye onto the electron
transport layer 3. Immersion of this electron transport layer 3
into the saturated acetonitrile solution of sensitizing dye was not
carried out.
[0213] In addition, as the electrolytic solution, an acetonitrile
solution containing 2,2,6,6-tetramethyl piperidine-1-oxyl at a
concentration of 1 M, LiTFSI at 0.5 M and N-methyl benzimidazole at
1.6 M was used.
[0214] Otherwise, a photoelectric element was prepared in a similar
manner to Example 1.
[0215] [Storage Property]
[0216] The storage properties of the photoelectric elements
obtained in Example 1 and Comparative Example 1 were evaluated.
[0217] First, each photoelectric element was irradiated with light
at 200 lux for 300 seconds (5 minutes) and the open-circuit voltage
of the photoelectric element was measured using Keithley 2400
source meter (manufactured by Keithley, Model 2400 general-purpose
source meter). Next, each photoelectric element was placed inside a
light-shielding container for 300 seconds (5 minutes) to measure
the open-circuit voltage of the photoelectric element similarly to
the above method.
[0218] The measurement results of the open-circuit voltage for
Example 1 are shown in FIG. 6, and the measurement results of the
open-circuit voltage for Comparative Example 1 are shown in FIG. 7,
respectively.
[0219] According to this result, open-circuit voltage maintenance
rate was 50% or greater for Example 1, a high storage ability. In
contrast, the open-circuit voltage maintenance rate was less than
1% for Comparative Example 1.
[0220] [Redox Potential Measurements]
[0221] Methods for measuring the redox potentials for the layers of
gaivi polymer of Examples 1 and 4 to 6, the layer of
polydecylviologen of Example 4, the layer of quinone polymer of
Example 5, the layer of polyimide of Example 6 are shown in the
following.
[0222] (Redox Potential Measurement for Galvi Polymer Layer)
[0223] Over a glass substrate with a transparent electro-conductive
film, a 100 nm-thick layer of galvi polymer was formed by
spincoating similarly to Example 4. Next, the first electrode 2
provided with the galvi polymer layer was impregnated with an
electrolytic solution to soak the electrolytic solution into the
voids within the galvi polymer layer. An acetonitrile solution of
perchloric acid tetrabutylammonium perchlorate at 0.1 mol/l was
used as the electrolytic solution. Then, when a platinum electrode
as the counter-electrode and Ag/AgCl electrode for the reference
electrode were used to prepare a half-cell to perform an evaluation
of the electric potential, the redox potential was 0 V.
[0224] (Redox Potential Measurement for Polydecylviologen
Layer)
[0225] A glass substrate with a transparent electro-conductive film
was immersed for 15 minutes in an aqueous solution of
polydecylviologen at a concentration of 0.1 N (pH10) to form a
polydecylviologen layer over the transparent electro-conductive
film. Next, the first electrode 2 provided with the
polydecylviologen layer was impregnated with an electrolytic
solution to soak the electrolytic solution into the voids within
polydecylviologen layer. An acetonitrile solution of perchloric
acid tetrabutylammonium perchlorate at 0.1 mol/l was used as the
electrolytic solution. Then, when a platinum electrode as the
counter-electrode and Ag/AgCl electrode for the reference electrode
were used to prepare a half-cell to perform an evaluation of the
electric potential, the redox potential of the polydecylviologen
layer was -0.4 V.
[0226] (Redox Potential Measurement for Layer of Quinone
Polymer)
[0227] Over a glass substrate with a transparent electro-conductive
film, a 100 nm-thick layer of quinone polymer was formed by
spincoating similarly to Example 5. Next, the first electrode 2
provided with the quinone polymer layer was impregnated with an
electrolytic solution to soak the electrolytic solution into the
voids within the quinone polymer layer. An acetonitrile solution of
perchloric acid tetrabutylammonium perchlorate at 0.1 mol/l was
used as the electrolytic solution. Then, when a platinum electrode
as the counter-electrode and Ag/AgCl electrode for the reference
electrode were used to prepare a half-cell to perform an evaluation
of the electric potential, the redox potential of the quinone
polymer layer was -0.8 V.
[0228] (Redox Potential Measurement for Layer of Polyimide)
[0229] Over a glass substrate with a transparent electro-conductive
film, a 100 nm-thick layer of polyimide layer r was formed by
spincoating similarly to Example 6: Next, the first electrode 2
provided with the polyimide layer was impregnated with an
electrolytic solution to soak the electrolytic solution into the
voids within the polyimide layer. An acetonitrile solution of
perchloric acid tetrabutylammonium perchlorate at 0.1 mol/l was
used as the electrolytic solution. Then, when a platinum electrode
as the counter-electrode and Ag/AgCl electrode for the reference
electrode were used to prepare a half-cell to perform an evaluation
of the electric potential, the redox potential of the polyimide
layer was -1.0 V.
[0230] [Evaluation Test]
[0231] While irradiating a region of 1 cm.sup.2 surface area in
planar view of the photoelectric element obtained in each Example
and Comparative Example with a light at 200 lux, the open-circuit,
voltage and the short-circuit current value of each photoelectric
element were measured by IV measurement using Keithley 2400 source
meter (Model 2400 general-purpose source meter manufactured by
Keithley). A fluorescent lamp (rapid fluorescence lamp, FLR20SW/M,
manufactured by Panasonic) was used as the light source, to carry
out measurements under environment an of 25.degree. C. In addition,
the evaluation of the photoelectric element was carried out under
conditions where of 1 cm.sup.2 photoelectric converting portion
received light. The results are shown Table 1 below.
TABLE-US-00001 TABLE 1 Open- Short- Electrifying material circuit
circuit Maximum Roughness voltage voltage output Species Forming
method Thickness factor Porosity (mV) (.mu.A/cm.sup.2)
(.mu.W/cm.sup.2) Example 1 -- -- -- -- -- 510 1.0 Example 2 -- --
-- -- -- 520 1.2 Example 3 -- -- -- -- -- 530 1.5 Example 4 -- --
-- -- -- 530 1.5 Example 5 -- -- -- -- -- 600 1.3 Example 6 -- --
-- -- -- 590 1.4 Example 7 -- -- -- -- -- 605 0.52 0.23 Example 8
-- -- -- -- -- 550 0.5 0.17 Example 1 Aggregation Formed at the
same 120 nm 110 40% 530 2.5 -- of ITO time as electron particles
transport layer Example 2 Rod-shaped Formed at the same 120 nm 150
60% 540 2.0 -- electro- time as electron conductive transport layer
material Example 3 Aggregation Formation of 3 .mu.m 500 40% 550 3.0
-- of SnO.sub.2 porous electro- particles conductive film (spincoat
method) Example 4 Aggregation Formation of 10 .mu.m 2000 40% 550
1.9 -- of SnO.sub.2 porous electro- particles conductive film
(spincoat method) Example 5 SnO.sub.2 fiber Formation of 1 .mu.m
200 80% 550 3.3 -- porous electro- conductive film
(electro-spinning method) Comparative -- -- -- -- -- 500 0.5 --
Example 1
[0232] As can be seen in Table 1, for each of the examples, the
open-circuit voltage value and the short circuit current value were
higher than those for the comparative examples, confirming that the
conversion efficiency was improved. Example 7, which contains an
azaadamantane-N-oxyl derivative within the hole transport layer 4
was found to obtain high photoelectric conversion efficiency
compared to Example 8. Examples 9 to 13, which have the
electro-conductive additive 8 present within the gel layer 6, were
found to obtain high photoelectric conversion efficiency.
EXPLANATION OF REFERENCE NUMERALS
[0233] 1 first substrate [0234] 2 first electrode [0235] 3 electron
transport layer [0236] 4 hole transport layer [0237] 5 second
electrode [0238] 6 gel layer [0239] 7 second substrate
* * * * *